CN102455683B - Number control device and friction compensation method - Google Patents

Abstract

The present invention provides a number control device and a friction compensation method. A friction force or a friction torque with high accuracy from a low-speed area to a high-speed area can be evaluated in a double-nut-precompression mode feeding driving mechanism, and the feeding driving mechanism is not limited to super-large-dimension ball rolling precompression mode. Therefore, the number control device can correct quadrant projection which reflects deflection of a movement track out of an instruction track. In the double-nut-precompression mode feeding driving mechanism, a ball rolling screw shaft rotates reversely for generating a first quadrant projection. The double-nut-precompression mode feeding driving mechanism generates a second quadrant projection after a worktable rotates reversely and moves for a preset amount. The number control device can estimate increase of the friction force which is generated in two periods in the double-nut-precompression mode through two approximate expressions.

Description

Numerical control device and friciton compensation method

Technical field

The present invention relates to a kind of numerical control device and friciton compensation method.

Background technology

Lathe is controlled motor in order to carry out two axle circular interpolation motions.Lathe cannot reverse immediately in the time of the sense of rotation reversion of motor.Reason is the frictional influence of feeding driving mechanism.If in the time carrying out circular arc cutting, quadrant changes (the moving direction reversion of moving body), the actual motion track of moving body is biased to the outside of instruction track.The phenomenon that motion track is biased to outside is quadrant projection, makes machining precision variation.

2008 No. 210273 disclosed control device of electric motor of communique of Japanese Patent Publication differentiate to obtain rate signal to the actual position signal of moving body.Control device of electric motor carries out integral operation to rate signal, generates the displacement signal from the position of moving body return motion direction and obtains absolute value.Control device of electric motor is obtained friction force or the friction torque rate of change with respect to displacement with the model that represents the relation between displacement and friction force or friction torque.Control device of electric motor multiplies each other to obtain the rate of change with respect to the time by the rate of change with respect to displacement and rate signal.Control device of electric motor carries out integral operation to the rate of change with respect to the time and comes estimated friction power or friction torque.Control device of electric motor is not subject to the impact of speed before and after return motion direction or acceleration and estimates friction force or friction torque.

Control device of electric motor is mainly supported the feeding driving mechanism of oversize ball precompressed mode.The feeding driving mechanism of oversize ball precompressed mode possesses a nut and ballscrew shaft.The feeding driving mechanism of double nut precompressed mode possesses two nuts and ballscrew shaft.In the feeding driving mechanism of double nut precompressed mode, ballscrew shaft reverses and produces first quadrant projection, produces second quadrant projection in the time that moving body has moved ormal weight.Control device of electric motor is not supported double nut precompressed mode and cannot be proofreaied and correct second quadrant projection.

The friction factor of lathe also has line slideway (linearguide) and bearing (bearing) except ballscrew shaft.Line slideway and bearing improve mechanical rigidity by applying high precompressed.Therefore, the friction torque characteristic in the time of reversion can change suddenly.Other friction factor is the seal member of oil sealing (oil seal) and movable smear metal cover.Oil sealing is installed on motor axial region.Oil sealing is used for preventing that cutting oil from entering motor interior.Seal member prevents that smear metal from entering ballscrew shaft and line slideway portion.

Seal member and oil sealing are elastomeric materials.Compared with friction torque when reversion and line slideway etc., change lentamente.Rubbing characteristics when lathe reversion is the synthetic of two kinds of reversion rubbing characteristicss.

Control device of electric motor only uses single tanh function for representing the model of displacement from the position of reversion and relation between friction torque.Control device of electric motor is not considered above-mentioned two kinds of reversion rubbing characteristicss.Therefore can produce error.Two kinds of reversion rubbing characteristicss are to have the characteristic that following two aspects change: the friction torque after reversion sharply change and reverse after the slow variation of friction torque.

Control device of electric motor uses the model that represents the relation between displacement and friction force or friction torque from the position of moving body return motion direction.Control device of electric motor uses a model, and obtains friction force or the friction torque rate of change with respect to displacement as the function of the displacement signal with absolute value representation.Control device of electric motor multiplies each other to calculate friction force or the friction torque rate of change with respect to the time by the above-mentioned rate of change with respect to displacement and above-mentioned rate signal.Control device of electric motor carries out integral operation to the rate of change with respect to the time and comes estimated friction power or friction torque.Therefore, become large in fireballing situation lower integral error, large thereby the error of the friction force estimating or friction torque becomes.

Summary of the invention

the problem that invention will solve

Even if the object of the present invention is to provide a kind of numerical control device and friciton compensation method that friction force from low-speed region to high-speed region or friction torque are proofreaied and correct quadrant projection that also can estimate accurately in the feeding driving mechanism of double nut precompressed mode.

The numerical control device of the first invention possesses feed mechanism, motor, position detecting mechanism, speed generating unit, speed detecting mechanism, torque generating unit, friction estimator, correction unit, the first friction estimator and the second friction estimator.Feed mechanism has ballscrew shaft and ball nut, for moving body is moved.Ball nut fit on is in ballscrew shaft.Moving body is fixed on ball nut.Motor is rotated driving to ballscrew shaft.Position detecting mechanism detects the position that utilizes the moving body that motor moves.Speed generating unit generates the consistent speed command of position command that the position of the detected moving body of position detecting mechanism is generated with control part.Speed detecting mechanism detects the speed of motor.Torque generating unit generates the consistent torque instruction of speed command that the detected speed of speed detecting mechanism is generated with speed generating unit.Friction estimator is estimated the friction force or the friction torque that after the sense of rotation reversion of motor, produce.Friction force or friction torque that correction unit estimates according to friction estimator are proofreaied and correct torque instruction.Ball nut is made up of a pair of ball nut.The first friction estimator is estimated the friction force being caused by feed mechanism or the friction torque that from the moving direction reversion of moving body, increase.The second friction estimator estimates that moving body after the moving direction reversion of moving body has moved after ormal weight the friction force or the friction torque that increase due to ballscrew shaft and a pair of ball nut.Friction estimator is carried out additive operation to the first friction estimator and the second friction estimator friction force or friction torque of estimating respectively.The feed mechanism of double nut precompressed mode the has had fit on ballscrew shaft of a pair of nut.Friction force or friction torque that the feed mechanism of double nut precompressed mode produces the friction force that caused by the structure of feed mechanism or friction torque and caused by the structure of the supporting device of moving body.The first friction estimator is estimated the friction force being caused by feed mechanism or the friction torque that from the moving direction reversion of moving body, increase.The second friction estimator estimates that moving body after the moving direction reversion of moving body has moved after ormal weight the friction force or the friction torque that increase due to ballscrew shaft and a pair of ball nut.Friction estimator is carried out additive operation to the friction force or the friction torque that are estimated by the first friction estimator and the second friction estimator.Therefore, numerical control device also can estimate accurately friction force or friction torque in the feed mechanism of double nut precompressed mode, therefore can proofread and correct quadrant projection.

In the numerical control device of the second invention, above-mentioned a pair of ball nut has multiple balls.Afore mentioned rules amount is that after the moving direction reversion of moving body, moving body moves in multiple balls distance when at least one ball contacts with a pair of ball nut and 3 of ballscrew shafts.In the feed mechanism of double nut precompressed mode, ball carries out 2 states that contact with a pair of nut and ballscrew shaft and carries out the alternately transformation of 3 states that contact with ball and a pair of nut and ballscrew shaft.Friction force or friction torque increase in the time that 2 contacts become 3 contacts at ball.Therefore, the second friction estimator can estimate moving body after the moving direction reversion of moving body and move after ormal weight the friction force or the friction torque that increase due to ballscrew shaft and a pair of ball nut.

The numerical control device of the 3rd invention possesses actual position estimation portion and calculating part.Actual position estimation portion estimates the physical location of the moving body corresponding with position command.The physical location that calculating part estimates according to actual position estimation portion calculates the displacement after the moving direction reversion of moving body.The first friction estimator and the second friction estimator are approximate expressions.Approximate expression is the displacement that calculates taking the calculating part formula as variable.Therefore friction force or friction torque that, numerical control device can easily calculate the friction force being caused by feed mechanism of increase from the moving direction reversion of moving body or friction torque and increase due to ballscrew shaft and a pair of ball nut.

In the numerical control device of the 4th invention, the approximate expression f of the first friction estimator ₁the approximate expression f of (x '), the second friction estimator ₂the amount of movement that (x ') reverses the friction force changing from the moving direction reversion of moving body or friction torque after moving direction with respect to moving body resolves into the second slope composition that the first slope composition and slope are less than this first slope composition.X ' is the displacement from moving direction backward position of above-mentioned moving body.F _c0friction force or the friction torque of the rising from reversion of the first slope composition.A ₀it is the rising distance constant of the first slope composition.A ₁it is the rising distance constant of the second slope composition.F _c1the kinetic force of friction of variation from the moving direction reversion of moving body or the total value of kinetic friction torque.F _c2the rear moving body of moving direction reversion that is moving body has moved the kinetic force of friction being caused by ballscrew shaft and a pair of ball nut or the kinetic friction torque that after ormal weight, increase.B is ormal weight.A ₂that moving body has moved the friction force of increase after ormal weight b or the rising distance constant of friction torque from the moving direction reversion of moving body.Sgn is-symbol function.The approximate expression f of the first friction estimator ₁the approximate expression f of (x '), the second friction estimator ₂(x ') be formula below.Therefore friction force or friction torque that, numerical control device can easily calculate the friction force being caused by feed mechanism of increase from the moving direction reversion of moving body or friction torque and increase due to ballscrew shaft and a pair of ball nut.

$f_1\left(x^{\′}\right)=f_{c0}(\tanh \left(\frac{\left|x^{\′}\right|}{a_0}\right)-\frac{1}{2})\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\′}}{\mathrm{dt}}\right)+(f_{c1}+\frac{f_{c2}}{2}-\frac{f_{c0}}{2})(2\tanh \left(\frac{\left|x^{\′}\right|}{a_1}\right)-1)\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\′}}{\mathrm{dt}}\right)$

$f_2\left(x^{\′}\right)=f_{c2}(\tanh \left(\frac{\left|x^{\′}\right|-b}{a_2}\right)-\frac{1}{2})\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\′}}{\mathrm{dt}}\right)$

$\left|x^{\&prime;}\right|-b<0\&DoubleRightArrow;f_2\left(x^{\&prime;}\right)=-\frac{f_{c2}}{2}\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

In the numerical control device of the 5th invention, the approximate expression f of the first friction estimator ₁the approximate expression f of (x '), the second friction estimator ₂the amount of movement that (x ') reverses the friction force changing from the moving direction reversion of moving body or friction torque after moving direction with respect to moving body resolves into the second slope composition that the first slope composition and slope are less than this first slope composition.X ' is the displacement from moving direction backward position of above-mentioned moving body.F _c0friction force or the friction torque of the rising from reversion of the first slope composition.A ₀it is the rising distance constant of the first slope composition.A ₁it is the rising distance constant of the second slope composition.F _c1the kinetic force of friction of variation from the moving direction reversion of moving body or the total value of kinetic friction torque.F _c2the rear moving body of moving direction reversion that is moving body has moved the kinetic force of friction being caused by ballscrew shaft and a pair of ball nut or the kinetic friction torque that after ormal weight, increase.B is ormal weight.A ₂that moving body has moved the friction force of increase after ormal weight b or the rising distance constant of friction torque from the moving direction reversion of moving body.Sgn is-symbol function.The approximate expression f of the first friction estimator ₁the approximate expression f of (x '), the second friction estimator ₂(x ') be formula below.Therefore friction force or friction torque that, numerical control device can easily calculate the friction force being caused by feed mechanism of increase from the moving direction reversion of moving body or friction torque and increase due to ballscrew shaft and a pair of ball nut.

$f_1\left(x^{\&prime;}\right)=f_{c0}(\frac{1}{2}-\exp \frac{-\left|x^{\&prime;}\right|}{a_0})\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)+(f_{c1}+\frac{f_{c2}}{2}-\frac{f_{c0}}{2})(1-2\exp \frac{-\left|x^{\&prime;}\right|}{a_1})\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

$f_2\left(x^{\&prime;}\right)=f_{c2}(\frac{1}{2}-\exp \frac{-\left(\right|x^{\&prime;}|-b)}{a_2})\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

$\left|x^{\&prime;}\right|-b<0\&DoubleRightArrow;f_2\left(x^{\&prime;}\right)=-\frac{f_{c2}}{2}\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

In the numerical control device of the 6th invention, the approximate expression f of the first friction estimator ₁the approximate expression f of (x '), the second friction estimator ₂the amount of movement that (x ') reverses the friction force changing from the moving direction reversion of moving body or friction torque after moving direction with respect to moving body resolves into the second slope composition that the first slope composition and slope are less than this first slope composition.X ' is the displacement from moving direction backward position of above-mentioned moving body.F _c0friction force or the friction torque of the rising from reversion of the first slope composition.A ₀it is the rising distance constant of the first slope composition.A ₁it is the rising distance constant of the second slope composition.F _c1the kinetic force of friction of variation from the moving direction reversion of moving body or the total value of kinetic friction torque.F _c2the rear moving body of moving direction reversion that is moving body has moved the kinetic force of friction being caused by ballscrew shaft and a pair of ball nut or the kinetic friction torque that after ormal weight, increase.B is ormal weight.A ₂that moving body has moved the friction force of increase after ormal weight b or the rising distance constant of friction torque from the moving direction reversion of moving body.Sgn is-symbol function.The approximate expression f of the first friction estimator ₁the approximate expression f of (x '), the second friction estimator ₂(x ') be formula below.Therefore friction force or friction torque that, numerical control device can easily calculate the friction force being caused by feed mechanism of increase from the moving direction reversion of moving body or friction torque and increase due to ballscrew shaft and a pair of ball nut.

$f_1\left(x^{\&prime;}\right)=f_{c0}(\tanh \left(\frac{\left|x^{\&prime;}\right|}{a_0}\right)-\frac{1}{2})\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)+(f_{c1}+\frac{f_{c2}}{2}-\frac{f_{c0}}{2})(2\tanh \left(\frac{\left|x^{\&prime;}\right|}{a_1}\right)-1)\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

$f_2\left(x^{\&prime;}\right)=f_{c2}(\frac{1}{2}-\exp \frac{-\left(\right|x^{\&prime;}|-b)}{a_2})\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

$\left|x^{\&prime;}\right|-b<0\&DoubleRightArrow;f_2\left(x^{\&prime;}\right)=-\frac{f_{c2}}{2}\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

In the numerical control device of the 7th invention, the approximate expression f of the first friction estimator ₁the approximate expression f of (x '), the second friction estimator ₂the amount of movement that (x ') reverses the friction force changing from the moving direction reversion of moving body or friction torque after moving direction with respect to moving body resolves into the second slope composition that the first slope composition and slope are less than this first slope composition.X ' is the displacement from moving direction backward position of above-mentioned moving body.F _c0friction force or the friction torque of the rising from reversion of the first slope composition.A ₀it is the rising distance constant of the first slope composition.A ₁it is the rising distance constant of the second slope composition.F _c1the kinetic force of friction of variation from the moving direction reversion of moving body or the total value of kinetic friction torque.F _c2the rear moving body of moving direction reversion that is moving body has moved the kinetic force of friction being caused by ballscrew shaft and a pair of ball nut or the kinetic friction torque that after ormal weight, increase.B is ormal weight.A ₂that moving body has moved the friction force of increase after ormal weight b or the rising distance constant of friction torque from the moving direction reversion of moving body.Sgn is-symbol function.The approximate expression f of the first friction estimator ₁the approximate expression f of (x '), the second friction estimator ₂(x ') be formula below.Therefore friction force or friction torque that, numerical control device can easily calculate the friction force being caused by feed mechanism of increase from the moving direction reversion of moving body or friction torque and increase due to ballscrew shaft and a pair of ball nut.

$f_1\left(x^{\&prime;}\right)=f_{c0}(\frac{1}{2}-\exp \frac{-\left|x^{\&prime;}\right|}{a_0})\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)+(f_{c1}+\frac{f_{c2}}{2}-\frac{f_{c0}}{2})(1-2\exp \frac{-\left|x^{\&prime;}\right|}{a_1})\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

$f_2\left(x^{\&prime;}\right)=f_{c2}(\tanh \left(\frac{\left|x^{\&prime;}\right|-b}{a_2}\right)-\frac{1}{2})\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

$\left|x^{\&prime;}\right|-b<0\&DoubleRightArrow;f_2\left(x^{\&prime;}\right)=-\frac{f_{c2}}{2}\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

In the numerical control device of the 8th invention, the approximate expression of the second friction estimator is formula below.X ' is the displacement from moving direction backward position of above-mentioned moving body.F _c2the rear moving body of moving direction reversion that is moving body has moved the kinetic force of friction being caused by ballscrew shaft and a pair of ball nut or the kinetic friction torque that after ormal weight, increase.B is ormal weight.A ₂that moving body has moved the friction force of increase after ormal weight b or the rising distance constant of friction torque from the moving direction reversion of moving body.Sgn is-symbol function.Therefore, numerical control device can easily calculate the friction force or the friction torque that increase due to ballscrew shaft and a pair of ball nut.

$f_2\left(x^{\&prime;}\right)=-\frac{f_{c2}}{2}\cos \left(\frac{\left|x^{\&prime;}\right|-b}{a_2}\mathrm{\&pi;}\right)\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

$\left|x^{\&prime;}\right|-b<0\mathrm{or}\left|x^{\&prime;}\right|-b-a_2>0\&DoubleRightArrow;f_2\left(x^{\&prime;}\right)=-\frac{f_{c2}}{2}\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

The friciton compensation method of the 9th invention is the method for being undertaken by numerical control device.Numerical control device possesses feed mechanism, motor and position detecting mechanism.Feed mechanism has ballscrew shaft and ball nut, for moving body is moved.Ball nut fit on is in ballscrew shaft.Friciton compensation method comprises that speed generates operation, speed and detects operation, torque and generate operation, friction and estimate that operation, correcting process, the first friction estimate that operation and the second friction estimate operation.Speed generates operation and generates the consistent speed command of position command that the position of the detected moving body of position detecting mechanism is generated with control part.Speed detects the speed of operation detection motor.Torque generates operation and generates the consistent torque instruction of speed command that the detected speed of speed detecting mechanism is generated with speed generating unit.The friction force or the friction torque that after the sense of rotation reversion of operation estimation motor, produce are estimated in friction.Friction force or friction torque that correcting process estimates according to friction estimator are proofreaied and correct torque instruction.Ball nut is made up of a pair of ball nut.The friction force being caused by feed mechanism or the friction torque that operation estimation increases from the moving direction reversion of moving body estimated in the first friction.The second friction estimates that operation estimates that moving body after the moving direction reversion of moving body has moved after ormal weight the friction force or the friction torque that increase due to ballscrew shaft and a pair of ball nut.Friction estimates that operation estimates that to the first friction operation and the second friction estimate that the operation friction force or the friction torque that estimate respectively carry out additive operation.The feed mechanism of double nut precompressed mode the has had fit on ballscrew shaft of a pair of nut.Friction force or friction torque that the feed mechanism of double nut precompressed mode produces the friction force that caused by the structure of feed mechanism or friction torque and caused by the structure of the supporting device of moving body.The friction force being caused by feed mechanism or the friction torque that operation estimation increases from the moving direction reversion of moving body estimated in the first friction.The second friction estimates that operation estimates that moving body after the moving direction reversion of moving body has moved after ormal weight the friction force or the friction torque that increase due to ballscrew shaft and a pair of ball nut.Friction estimation operation is carried out additive operation to estimated friction force or friction torque that operation and the second friction estimation operation estimate by the first friction.Therefore,, even if friciton compensation method also can estimate accurately friction force or friction torque in the feed mechanism of double nut precompressed mode, therefore can proofread and correct quadrant projection.

Brief description of the drawings

Fig. 1 is the figure that represents a part for the structure of lathe 20.

Fig. 2 is the block diagram that represents the detailed structure of numerical control device 10 and feed mechanism.

Fig. 3 is the cut-open view of feeding driving mechanism A.

Fig. 4 is the cut-open view of the periphery of the ball 37 in feeding driving mechanism A.

Fig. 5 is the cut-open view of feeding driving mechanism B.

Fig. 6 is the figure that represents the contact condition of the ball 47 of feeding driving mechanism B.

Fig. 7 is the figure obtaining after the error between desirable arc track and the actual path of feeding driving mechanism A is amplified.

Fig. 8 is the figure obtaining after the error between desirable arc track and the actual path of feeding driving mechanism B is amplified.

Fig. 9 represents the motor torque of feeding driving mechanism A and the chart from the relation between the distance of backward position.

Figure 10 represents the motor torque of feeding driving mechanism B and the chart from the relation between the distance of backward position.

Figure 11 is the figure that represents the relation between worktable displacement amount and the friction torque of feeding driving mechanism A.

Figure 12 is the figure that represents the relation between worktable displacement amount and the friction torque of feeding driving mechanism B.

Figure 13 is the block diagram that represents the structure of friciton compensation device 13.

Figure 14 is the figure of the relation between worktable displacement amount and the friction torque while representing only to use the Section 1 of formula (1) to carry out estimated friction torque as approximate expression.

Figure 15 is the figure of the relation between worktable displacement amount and the friction torque while representing only to use formula (1) to carry out estimated friction torque as approximate expression.

Figure 16 is the figure of the relation between worktable displacement amount and the friction torque while representing that use formula of the present invention (3) (formula (1)+formula (2)) is carried out estimated friction torque as approximate expression.

Figure 17 is the figure of the relation between worktable displacement amount and the friction torque while representing that use formula of the present invention (3) (formula (4)+formula (5)) is carried out estimated friction torque as approximate expression.

Figure 18 is the figure of the relation between worktable displacement amount and the friction torque while representing that use formula of the present invention (3) (formula (1)+formula (6)) is carried out estimated friction torque as approximate expression.

Figure 19 is the figure obtaining after the error between desirable arc track and the actual path of example 2,3,6 is amplified.

Figure 20 is the block diagram of the structure while representing that the control module patent documentation 1 recorded by object of the present invention changes.

The figure of the relation between worktable displacement amount and friction torque when Figure 21 is the friction torque while representing to utilize compensation way 1 and compensation way 2 to estimate non-high speed motion.

The figure of the relation between worktable displacement amount and friction torque when Figure 22 is the friction torque while representing to utilize compensation way 1 and compensation way 2 to estimate high speed motion.

Figure 23 is the figure of the relation between worktable displacement amount and the friction torque while representing that use of the present invention (formula (1)+formula (5)) carrys out estimated friction torque as approximate expression.

Figure 24 is the figure of the relation between worktable displacement amount and the friction torque while representing that use of the present invention (formula (4)+formula (2)) carrys out estimated friction torque as approximate expression.

Embodiment

Embodiments of the present invention are described with reference to the accompanying drawings.Numerical control device 10 shown in Fig. 1 is embodiments of the present invention.The axle that numerical control device 10 is controlled lathe 20 according to the indicated path of job sequence moves, and the workpiece being fixed on worktable 3 is cut.

An example of the table mechanism of lathe 20 is described with reference to Fig. 1.Table mechanism possesses pedestal 1, middle worktable 50 and worktable 3.Pedestal 1 has rectangular shape.Middle worktable 50 moves on pedestal 1.Worktable 3 moves on middle worktable 50.Worktable 3 is examples for moving body of the present invention.

Pedestal 1 has a pair of line slideway 6A.A pair of line slideway 6A is along a middle worktable 50 of direction of principal axis guiding.Ballscrew shaft 4A and nut (omitting diagram) are disposed between a pair of line slideway 6A.Middle worktable 50 is fixed on nut.Middle worktable 50 has a pair of line slideway 6B on top.Line slideway 6B along with the orthogonal direction of above-mentioned direction of principal axis guiding worktable 3.Ballscrew shaft 4B and nut 5 (with reference to Fig. 2) are disposed between a pair of line slideway 6B.

As shown in Figure 2, worktable 3 possesses slide block 51 in bottom.Slide block 51 slides on the track 61 of line slideway 6B.Pair of bearing 7 rotating bearing ball lead screw shaft 4B.Pair of bearing 7 is fixed on middle worktable 50.Bearing seat 7 has bearing 8 in inside.Middle worktable 50 possesses slide block (omitting diagram) in lower end.Slide block is upper slip of track (omitting diagram) of line slideway 6A.

Pair of bearing (omitting diagram) rotating bearing ball lead screw shaft 4A.Pair of bearing is fixed on pedestal 1.Bearing seat has bearing (omitting diagram) in inside.

As shown in Figure 1, pedestal 1 is at upper support motor 2A.The axle of motor 2A is connected by shaft coupling (not shown) with ballscrew shaft 4A.Motor 2A has oil sealing (not shown) around axial region.

As shown in Figure 2, middle worktable 50 is at overhang bracket motor 2B.The axle of motor 2B is connected by shaft coupling 9 with ballscrew shaft 4B.Motor 2B has oil sealing 52 around axial region.Worktable 3 has fixed cover 53 at two ends.Seal member 55 is fixed on the end of a side contrary with worktable side end of movable hood 54.Seal member 55 is formed by rubber.Seal member 55 prevents that smear metal etc. from entering between fixed cover 53 and movable hood 54.

Feeding driving mechanism 56 makes worktable 3 move along a direction of principal axis.Feeding driving mechanism 56 possesses ballscrew shaft 4B and nut 5.The structure of feeding driving mechanism that in the middle of making, worktable 50 moves along a direction of principal axis is identical with the structure of the feeding driving mechanism 56 of worktable 3.The feed mechanism of worktable 3 at least comprises feeding driving mechanism 56, line slideway 6B, slide block 51, motor 2B, shaft coupling 9, oil sealing 52, movable hood 54, seal member 55, bearing seat 7.

The structure of logarithm value control device 10 describes.As shown in Figure 1, numerical control device 10 is connected with motor 2A, 2B.By the driving of motor 2A, 2B, worktable 3 moves along two direction of principal axis.

Rotatablely moving of motor 2A, 2B is transformed to the translatory movement of worktable 3 on two direction of principal axis by each ballscrew shaft 4A, 4B and each nut 5.Numerical control device 10 is controlled position, speed and the acceleration that motor 2A, 2B control worktable 3.

As shown in Figure 2, rotary encoder (rotary encoder) 60 is arranged on motor 2A, 2B.Fig. 2 does not illustrate the rotary encoder 60 of motor 2A, motor 2A side.Rotary encoder 60 detects the position of motor 2A, 2B.Numerical control device 10 comes the position of evaluation work platform 3 according to the pitch of the position of motor 2A, 2B, ballscrew shaft 4A, 4B (interval of ridge).

Position command signal is outputed to positioner 11 by host controller.The position detection signal of motor 2A, 2B is outputed to positioner 11 by rotary encoder 60.Positioner 11 generates and makes the position command signal speed command signal consistent with position detection signal and impose on speed control 12.Differentiator 16 is transformed to position detection signal speed detection signal and imposes on speed control 12.

Speed control 12 generates and makes the speed command signal torque instruction signal consistent with speed detection signal and impose on totalizer 14.Friciton compensation device 13 generates friciton compensation signal and imposes on totalizer 14 according to the position command signal from host controller.Friciton compensation signal is the signal that the friction force to producing in the time that the sense of rotation of motor 2A, 2B is reversed compensates.Totalizer 14 is carried out additive operation to the torque instruction signal from speed control 12 with from the friciton compensation signal of friciton compensation device 13.The torque instruction signal after friciton compensation is imposed on current control amplifier 15 by totalizer 14.Current control amplifier 15 is brought into play function as torque controller.Current control amplifier 15 controls to produce to the electric current of motor 2A, 2B the torque of the torque instruction signal after faithful to friciton compensation of trying one's best.

The structure of positioner 11, speed control 12, totalizer 14, current control amplifier 15, differentiator 16 and action be many weeks.Therefore, by with the structure of friciton compensation device 13 of the present application direct correlation and the principle of action centered by describe.

Feeding driving mechanism has the friction force being caused by the first sources of friction and the second sources of friction respectively.The friction force being caused by the first sources of friction is the precompressed of the nut portions of precompressed, the ballscrew shaft of the slide block of line slideway, the precompressed of bearing.Precompressed is higher, higher as the rigidity of feeding driving mechanism, and friction force is also larger.The friction force being caused by the second sources of friction is the sliding resistance of the seal of oil sealing 52, movable hood 54.When sealing improves, it is large that friction force becomes.

Friction force sharply changes in the time of the direction of motion reversion of worktable 3.The direction of motion of worktable 3 is the sense of rotation reversion of ballscrew shaft 4A, 4B while reversion time.For example, two orthogonal axles of numerical control device 10 use carry out above-mentioned circular interpolation and move to carry out circular arc cutting.Sometimes control system cannot be tackled the variation of friction force.The figure on the top of Fig. 1 represents the error between desirable arc track and actual path.The part 71～74th impaling with ellipse, quadrant projection.Friciton compensation device 13 estimates that the friction force in direction of motion when reversion of worktable 3 compensates accurately.Therefore, numerical control device 10 can reduce quadrant projection as much as possible.

Quadrant projection is caused by the variation of the friction force producing in feeding driving mechanism.The generation type of quadrant projection is according to the precompressed mode of ballscrew shaft and difference.The structure and characteristics difference of the precompressed mode to ballscrew shaft describes.The precompressed mode of ballscrew shaft comprises oversize ball precompressed mode and double nut precompressed mode.

As shown in Figure 3, the feeding driving mechanism A of oversize ball precompressed mode is for to utilize single nut 35 (hereinafter referred to as nut 35) to apply the mode of precompressed.Nut 35 is ball nuts.Nut 35 possesses ball 37 in inside.As shown in Figure 4, ball 37 carries out all the time at 4 with nut 35 and ballscrew shaft 34 and contacts.The size that oversize ball precompressed mode is characterised in that nut 35 is compared with little and be suitable for underload.Therefore, junior machine etc. adopts oversize ball precompressed mode.

As shown in Figure 5, the feeding driving mechanism B of double nut precompressed mode has two nuts 45,46.Nut the 45, the 46th, ball nut.Packing ring 48 is between nut 45,46.As shown in Fig. 6 (a), (b), (c), ball 47 and nut 45 (omitting diagram in Fig. 6), 46 moving direction correspondingly move.Ball 47 carries out at 2 with nut 45,46 and ballscrew shaft 44 and contacts or 3 contacts, changes at any time.Hollow arrow in Fig. 6 represents the sense of rotation of ball 47.

For example, as shown in Fig. 6 (a), nut 46 moves to a direction.Ball 47 contacts on one point with nut 46 and contacts at 2 with ballscrew shaft 44, therefore carries out 3 contacts.As shown in Fig. 6 (b), in the way of moving direction being reversed in nut 46.Ball 47 contacts on one point with nut 46 and contacts on one point with ballscrew shaft 44, therefore carries out 2 contacts.Therefore, contact and compare less traction with 3.As shown in Fig. 6 (c), nut 46 moves moving direction reversion round about.Ball 47 contacts and contacts on one point with ballscrew shaft 44 at 2 with nut 46, therefore carries out 3 contacts.Therefore, friction becomes large again.Double nut precompressed mode is characterised in that rigidity is high.Therefore, large-scale lathe etc. adopts double nut precompressed mode.

The impact of the precompressed mode that ballscrew shaft is described on quadrant projection.Having investigated in the case of using drives each numerical control device of controlling to carry out the error with respect to ideal trajectory circular interpolation motion to feeding driving mechanism A, B.

Fig. 7, Fig. 8 are the figure obtaining after the error between desirable arc track and actual path is amplified.Speed of feed is 3m/min, and instruction radius is 25mm.One scale is 5 μ m.

Trajectory error is quadrant projection.In the result of Fig. 7 and Fig. 8, quadrant projection all occurs near 0 °, 90 °, 180 °, 270 °.The direction of motion of X-axis is located to reverse at 0 ° and 180 °.The direction of motion of Y-axis is located to reverse at 90 ° and 270 °.Near quadrant projection servo-drive system each backward position shows on arc track and obtains for the response of change in friction force.Friction force when friction force is direction of motion reversion.

As shown in Figure 7, in feeding driving mechanism A, quadrant projection is one.Feeding driving mechanism A is oversize ball precompressed mode.As shown in Figure 8, in feeding driving mechanism B, quadrant projection is two.Feeding driving mechanism B is double nut precompressed mode.Reason is as follows.The impact of friction when first quadrant projection is quadrant change.Second quadrant projection be ball with nut and ballscrew shaft between the impact that contacts the frictions that increase in the time that 2 contacts become 3 contacts.

The characteristic of the frictional resistance while having investigated the reversion in ballscrew shaft individuality.Fig. 9, Figure 10 are the chart of ballscrew shaft from the distance of backward position and the relation of motor torque [Nm].

As shown in Figure 9, in oversize ball precompressed mode, motor torque becomes invariable quickly after rising after reversion.As shown in figure 10, in double nut precompressed mode, motor torque becomes invariable after rising a little after reversion, again becomes afterwards invariable after mild rising.During carrying out 2 contacts from backward position balling-up, motor torque becomes invariable after rising a little.Ball is the state of 3 contacts from the state-transition of 2 contacts.In these cases, the state of 2 contacts is to mix to exist with 3 states that contact.Therefore, motor torque rises gently.Afterwards, all balls all become 3 contacts.Therefore, motor torque becomes maximal value and is invariable.

Relation between worktable displacement amount and friction torque when Figure 11, Figure 12 represent that lathe carries out small arc operation.Speed of feed is 5mm/min, and instruction radius is 0.1mm.In small arc operation, friction force is not subject to the impact of speed and acceleration.

As shown in figure 11, in oversize ball precompressed mode, motor torque presents non-linear spring characteristic after direction of motion reversion.In the time that displacement is increased to a certain degree, motor torque becomes the value of constant.The track of motor torque is depicted magnetic hysteresis loop.As shown in figure 12, in double nut precompressed mode, the position of motor torque 0.065mm after direction of motion reversion is with mild step-like changing.Step-like variation is that quadrant projection is the reason of two.Numerical control device 10 is conceived to the rubbing characteristics of double nut precompressed mode.Numerical control device 10 can compensate two quadrant projections by estimating accurately friction force or friction torque.

The detailed structure and the friciton compensation method of utilizing friciton compensation device 13 of friciton compensation device 13 are described with reference to Figure 13.Friciton compensation device 13 at least possesses actual position estimation portion 21, differentiator 22, sign-inverted test section 23, integrator 24, the first rubbing characteristics estimator 26, the second rubbing characteristics estimator 27, totalizer 28, operating lag compensation section 29.The first rubbing characteristics estimator 26, the built-in absolute value calculating part of the second rubbing characteristics estimator 27 and polarity calculating part.Absolute value calculating part is obtained the absolute value of inputted signal.Polarity calculating part is obtained the polarity of inputted signal being carried out to the signal obtaining after time diffusion computing.

Position command signal is input to actual position estimation portion 21 by host controller.Actual position estimation portion 21 is used the model of the servo-control system of the feed motion of carrying out worktable 3.Actual position estimation portion 21 estimates that the physical location of the worktable 3 corresponding with position command signal generates actual position signal.Actual position estimation portion 21 for example also can be made up of first order lag element etc.Differentiator 22 is connected with actual position estimation portion 21.Differentiator 22 is differentiated to actual position signal and the signal obtaining is exported as rate signal.Sign-inverted test section 23 and integrator 24 are connected with differentiator 22.

Whether the symbol of sign-inverted test section 23 detection speed signals reverses.Sign-inverted test section 23 is exported reset signal.Integrator 24 carries out integral operation to rate signal and reduces actual position signal.Integrator 24 in the time that each sign-inverted test section 23 is exported reset signal by integrated value zero clearing.Integrator 24 generates the signal of the displacement from the position of worktable 3 return motion directions.

The first rubbing characteristics estimator 26 and the second rubbing characteristics estimator 27 are connected with integrator 24.The first rubbing characteristics estimator 26 is used approximate expression 1 described later.The first rubbing characteristics estimator 26 is obtained friction torque f ₁(x ') [Nm].Friction torque f ₁from worktable reversion, increase.The second rubbing characteristics estimator 27 is used approximate expression 2 described later.The second rubbing characteristics estimator 27 is obtained friction torque f ₂(x ') [Nm].Friction torque f ₂worktable 3 reverse aftertable 3 moved ormal weight after increase.Totalizer 28 is connected with the first rubbing characteristics estimator 26 and the second rubbing characteristics estimator 27.

Totalizer 28 is to f ₁(x ') and f ₂(x ') carries out additive operation.Operating lag compensation section 29 is connected with the output terminal of totalizer 28.Operating lag compensation section 29 is made up of the inverse function of transport function.Transport function obtains the characteristic model of the torque from torque instruction signal to motor 2 actual outputs.Torque instruction signal is input to current control amplifier 15 (with reference to Fig. 2).Operating lag compensation section 29 is carried out multiplying to the friction torque estimating and is generated friciton compensation signal.

Approximate expression 1 to the first rubbing characteristics estimator 26, the approximate expression 2 of the second rubbing characteristics estimator 27 describe.Present embodiment is as the various parameters of giving a definition.

F (x ')=total friction torque [Nm]

F ₁the friction torque [Nm] of (x ')=increase from worktable reversion

F ₂(x ')=worktable reversion aftertable has moved the friction torque [Nm] increasing after ormal weight

F _c0the friction torque [Nm] of the first slope composition rising from reversing when=amount of movement by the friction torque changing from worktable reversion after with respect to worktable reversion resolves into two kinds of slope compositions

A ₀the rising distance constant [mm] of=above-mentioned the first slope composition

A ₁the rising distance constant [mm] of=above-mentioned the second slope composition

F _c1the total value [Nm] of=kinetic friction torque of variation from worktable reversion

F _c2after the reversion of=worktable, move the kinetic friction torque being caused with a pair of ball nut by ballscrew shaft (the kinetic friction torque of (contact) when ballscrew shaft is stablized with nut) [Nm] increasing after afore mentioned rules amount at 3

A ₂=worktable reversion aftertable has moved the rising distance constant [mm] of the friction torque increasing after ormal weight

After the reversion of b=worktable, arrive f ₂(x ') distance [mm] till starting to increase

The displacement from direction of motion backward position [mm] of x '=worktable

Sgn=sign function

If sgn is+1 in the time of dx '/dt > 0, is 0 in the time of dx '/dt=0, in the time of dx '/dt < 0, be-1.

In the circular interpolation B-H loop in when motion, a has been shown carrying out shown in Figure 16 under double nut mode ₁, a ₂, f _c1, f _c2, b.The slope of the slope ratio second slope composition of the first slope composition is steep.

Approximate expression 1 is as follows.

·f ₁(x’)＝f _c0{tanh(|x’|/a ₀)-1/2}sgn(dx’/dt)+(f _c1+f _c2/2-f _c0/2){2tanh(|x’|/a ₁)-1}sgn(dx’/dt)…(1)

In the approximate expression of recording at patent documentation 1, tanh function is one group.The present invention combines two groups of different tanh functions of constant.Reason is in order to tackle this two side of the first friction factor and the second friction factor.The first friction factor is when reversion rubbing characteristics line slideway jumpy etc.The first slope is caused by the first friction factor.The second friction factor is the oil sealing of slow variation compared with the first friction factor etc.The second slope composition is caused by the second friction factor.

Approximate expression 2 is as follows.

·f ₂(x’)＝f _c2{tanh((|x’|-b)/a ₂)-1/2}sgn(dx’/dt)…(2)

Be located at | x ' | in the situation of-b < 0, f ₂(x ')=-f _c2/ 2sgn (dx '/dt).

(2) formula is for tackling the friction of double nut precompressed mode.The friction of double nut precompressed mode increases after nut reverses and moved ormal weight.

Utilize (1) formula, (2) formula, the approximate expression 3 of total friction torque f (x ') is following formula.

·f(x’)＝f ₁(x’)+f ₂(x’)…(3)

In approximate expression 1,2, also can replace tanh function with exp function.Approximate expression 1,2 for example also can represent as follows.A with formula (1) ₀, a ₁, formula (2) a ₂relatively choose a of formula (4) ₀, a ₁, formula (5) a ₂appropriate value.Therefore, formula (4) (5) can be depicted the curve roughly the same with formula (1) (2).

·f ₁(x’)＝f _c0{1/2-exp(-|x’|/a ₀)}sgn(dx’/dt)+(f _c1+f _c2/2-f _c0/2){1-2exp(-|x’|/a ₁)}sgn(dx’/dt)…(4)

·f ₂(x’)＝f _c2{1/2-exp{-(|x’|-b)}/a ₂}sgn(dx’/dt)…(5)

Be located at | x ' | in the situation of-b < 0, f ₂(x ')=-f _c2/ 2sgn (dx '/dt).

Can also represent as follows approximate expression 2 with cos function.In approximate expression 2, | x ' | near-b=0, rise and become mild.Approximate expression 2 can be depicted the curve that more approaches measured data.

·f ₂(x’)＝-f _c2/2cos{{(|x’|-b)/a ₂}π}sgn(dx’/dt)…(6)

Be located at | x ' |-b < 0 or | x ' |-b-a ₂in the situation of > 0, f ₂(x ')=-f _c2/ 2sgn (dx '/dt).

In order to confirm the effect of the numerical control device 10 with friciton compensation device 13, example 1～5 is compared.Example 1 is to apply the situation that friciton compensation method has in the past been carried out circular interpolation motion.Example 2 is only to apply approximate expression 1 of the present invention to have carried out the situation that circular interpolation moves.Example 3 is situations that formula (1) is used as to approximate expression 1, formula (2) has been carried out to circular interpolation motion as approximate expression 2 of the present invention.Example 4 is situations that formula (4) is used as to approximate expression 1, formula (5) has been carried out to circular interpolation motion as approximate expression 2 of the present invention.Example 5 is situations that formula (1) is used as to approximate expression 1, formula (6) has been carried out to circular interpolation motion as approximate expression 2 of the present invention.The approximate expression that example 1 is recorded with reference to TOHKEMY 2008-210273 communique, is only used the Section 1 of the formula (1) that the present invention records, i.e. f _c0tanh (| x ' |/a ₀)-1/2}sgn (dx '/dt) is as the approximate expression of identical meanings.It is the circular interpolation motion that 5mm/min, instruction radius are 0.1mm that example 1～5 carries out speed of feed.Result relation between worktable displacement amount and motor torque and measured data being compared and obtain is as follows.

In example 1,2, the definition of the parameter of the first rubbing characteristics estimator 26 of friciton compensation device 13, the approximate expression that the second rubbing characteristics estimator 27 is used is also identical with above-mentioned definition.

The result of example 1 is described with reference to Figure 14.In Figure 14, represent measured value with thick line, represent the value of utilizing approximate expression to calculate with fine rule.Parameter is chosen the value that can be similar to the rising characteristic of measured data after reversion.In this example, f _c0=0.9, a ₀=0.0025.As shown in figure 14, the slope of this ascending amount of 0.9Nm of the value of the approximate expression of motor torque and the initial first stage of measured value matches.Measured value is mild rising after the rising of first stage, in the rising that subordinate phase occurs from approximately 70 μ m after reversing again.Approximate expression is steady state value, therefore misfits with measured value.Reason is as follows: the sharply friction that the approximate expression in the past of patent documentation 1 can only be tackled after the caused reversions such as line slideway changes this single characteristic.Therefore, approximate expression in the past cannot be proofreaied and correct the rubbing characteristics of oil sealing etc. and the rubbing characteristics of double nut precompressed mode.The rubbing characteristics of oil sealing etc. slowly changes afterwards in reversion.The rubbing characteristics of double nut precompressed mode increases after reversion back nut has moved predetermined distance.

As shown in Figure 14, Figure 15, the measured value in example 1,2 and the result of approximate expression are poor by existing in the torque value before reversion.Actual torque instruction is the output of speed control 12 and the output sum of approximate expression.Control and make torque instruction consistent with the value of measured value.Speed control 12 is approximately-0.175Nm of output before the reversion at-100 μ m places for example.Actual torque instruction is that approximate expression is offset downward to the value obtaining after 0.175Nm.Therefore, the elevated portion office approximate expression of the friction torque after reversion is consistent with measured value.

The result of example 2 is described with reference to Figure 15.Example 2 has only used formula of the present invention (1).In Figure 15, be also to represent measured value with thick line, represent the value of utilizing approximate expression to calculate with fine rule.Parameter is chosen the value of the rising characteristic of first stage after the reversion that can be similar to measured data.In this example, f _c0=0.9, a ₀=0.0025, f _c1=0.625, a ₁=0.031.As shown in figure 15, utilize the combination of two groups of tanh functions that the friction after reversing is changed and is similar to.In from reversion, the friction to first stage of 60 μ m increases, measured value is consistent with approximate expression.In the friction of subordinate phase increases, measured value and approximate expression are inconsistent.Therefore,, although example 2 can be tackled the torque characteristics that reverse slowly such as oil sealing, the friction that cannot tackle two stages of double nut precompressed mode increases.

The result that uses approximate expression 3 of the present invention is described.Figure 16 is the situation that in example 3, approximate expression 1 and approximate expression 2 are all used tanh function.Figure 17 is the situation that in example 4, approximate expression 1 and approximate expression 2 are all used exp function.Figure 18 be in example 5 use formula (1) as approximate expression 1 and use the cos function of formula (6) as the situation of approximate expression 2.Represent measured value with thick line, represent the value of utilizing approximate expression to calculate with fine rule.In example 3～5, parameter is chosen the value that can be similar on the whole measured data.In example 3, f _c0=0.9, a ₀=0.0025, f _c1=0.45, a ₁=0.031, f _c2=0.35, a ₂=0.02, b=0.075.In example 4, f _c0=0.9, a ₀=0.0018, f _c1=0.45, a ₁=0.022, f _c2=0.35, a ₂=0.014, b=0.075.In example 5, f _c0=0.9, a ₀=0.0025, f _c1=0.45, a ₁=0.031, f _c2=0.35, a ₂=0.05, b=0.06.As shown in Figure 16, Figure 17, the value of approximate expression of the present invention 3 of motor torque and the rising of the initial first stage of measured value coincide, and also coincide with the rising of subordinate phase.Approximate expression 3 is tackled for the first time, this friction of twice for the second time increases.Therefore, example 3,4 can be tackled the friction in two stages of double nut precompressed mode increases.

The difference of the approximate expression of example 3,4 is to change a ₀, a ₁, a ₂value and obtain roughly equal curve.Therefore, utilize by approximate expression 1 be made as formula (1), combination that approximate expression 2 is made as to formula (5) is used approximate expression 3 and the result that obtains is also the result of calculation that is similar to well measured value.Utilize by approximate expression 1 be made as formula (4), combination that approximate expression 2 is made as to formula (2) is used approximate expression 3 and the result that obtains is also the result of calculation that is similar to well measured value.

As shown in figure 18, example 5 has used cos function in the rising of the friction of subordinate phase.Therefore, rising more more level and smooth than example 3,4, is the value that more approaches measured value.Utilize using approximate expression 1 as formula (4), using approximate expression 2 as formula, the combination of (6) is used approximate expression 3 and the result of calculation that obtains is also similarly the result of calculation that is similar to well measured value with example 5.

In order to investigate the reduction effect of the quadrant projection in example 2,3, investigate the error between desirable arc track and actual track.Actual path shown in Figure 19 is that speed of feed is made as to 6m/min, instruction radius is made as to the arc track in the situation of 50mm.Example 6 is comparative example.Example 6 is the situations of not carrying out friciton compensation completely.In Figure 19, represent example 2 with long dotted line, represent example 3 with solid line, represent example 6 with short dash line.

In example 6, produce two quadrant projections.Two quadrant projections are the characteristic of double nut precompressed mode.A disappearance in example 2 in two quadrant projections.Second residual.2 utilizations of example are only tackled the approximate expression 1 of first stage and have been carried out friciton compensation.Only the approximate expression after reply reversion can be tackled oversize ball precompressed mode, but can not tackle double nut precompressed mode.Therefore, only the approximate expression after reply reversion cannot be eliminated quadrant projection, therefore cannot obtain good machining precision.

In example 3, quadrant projection substantially all disappears.Example 3 utilizes approximate expression 3 of the present invention to carry out friciton compensation.Reason is as follows: by utilizing approximate expression 1,2, which in the friction force no matter producing in two stages after axle reversion can both be estimated accurately.Therefore, no matter be the feeding driving mechanism of oversize ball precompressed mode or the feeding driving mechanism of double nut precompressed mode, numerical control device 10 can both be supported.Numerical control device 10 can also support the to reverse lathe of rubbing characteristics Composite.Therefore, numerical control device 10 can effectively improve the machining precision of workpiece.

Rotary encoder 60 is examples for position detection unit of the present invention.Positioner 11 is examples for speed generation unit of the present invention.Differentiator 16 is examples for speed detection unit of the present invention.Speed control 12 is examples for torque generation unit of the present invention.Actual position estimation portion 21 is examples for actual position estimation of the present invention unit.Friciton compensation device 13 is examples for friction estimation unit of the present invention.Operating lag compensation section 29 is examples for operating lag correcting unit of the present invention.The second rubbing characteristics estimator 27 is examples for the second friction estimation unit of the present invention.The first rubbing characteristics estimator 26 is examples for the first friction estimation unit of the present invention.Totalizer 28 is examples for additive operation of the present invention unit.

As described above, the numerical control device 10 of present embodiment and friciton compensation method not only can be supported the feeding driving mechanism of oversize ball precompressed mode, can also fully support the feeding driving mechanism of double nut precompressed mode.In double nut precompressed mode, ball carries out at 2 according to the moving direction of nut and nut and ballscrew shaft and contacts or 3 contacts.In double nut precompressed mode, ballscrew shaft reverses and produces first quadrant projection, produces second quadrant projection in the time that worktable 3 has been moved further ormal weight.Friciton compensation method in the past is only supported oversize ball precompressed mode.Friciton compensation method in the past cannot be eliminated peculiar second the quadrant projection of double nut precompressed mode.Present embodiment is used two approximate expressions, can estimate accurately the rising of the friction force producing in two stages the in the situation that of double nut precompressed mode.First quadrant projection is caused by the rubbing characteristics after reversion.Rubbing characteristics after reversion comprise reversion after rubbing characteristics sharply change and from reversing rubbing characteristics slowly change.The former example is that the rubbing characteristics being caused by line slideway changes.The latter's a example is that the rubbing characteristics being caused by the oil sealing of motor axial region changes.Present embodiment considers that two kinds of rubbing characteristicss can be used two approximate expressions.Present embodiment not only can be eliminated first quadrant projection, can also eliminate reliably second quadrant projection in the past cannot eliminating.Present embodiment also can effectively be eliminated quadrant projection under double nut precompressed mode, with oil sealing time.Present embodiment can improve machining precision reliably.

The present invention is not limited to above-mentioned embodiment, can carry out various changes.For example, in the friciton compensation device 13 of above-mentioned embodiment, the first rubbing characteristics estimator 26 use approximate expressions 1 are calculated friction torque f ₁(x ').The second rubbing characteristics estimator 27 use approximate expressions 2 are calculated friction torque f ₂(x ').Friciton compensation device 13 utilizes approximate expression 3 to f ₁(x '), f ₂(x ') carries out additive operation and calculates total friction torque f (x ').Friciton compensation device 13 carries out additive operation by total friction torque f (x ') with torque.

For example, also can revise so that its object according to the invention 2008 No. 210273 disclosed friciton compensation devices of communique of Japanese Patent Publication.Friciton compensation device can compensate point friction force of two stage increases by two approximate expressions 5,6 with different from the embodiment described above.Structure and action to friciton compensation device 106 describe.Friciton compensation device 106 is variation of friciton compensation device 13.

The structure of friciton compensation device 106 is described with reference to Figure 20.A part of structure that friciton compensation device 106 possesses is identical with the friciton compensation device 13 shown in Figure 13.Friciton compensation device 106 possesses actual position estimation portion 21, differentiator 22, sign-inverted test section 23, integrator 24, totalizer 28, operating lag compensation section 29.Friciton compensation device 106 possesses the 3rd rubbing characteristics estimator 56, the 4th rubbing characteristics estimator 57.The 3rd rubbing characteristics estimator 56 is used for replacing the first rubbing characteristics estimator 26.The 4th rubbing characteristics estimator 57 is used for replacing the second rubbing characteristics estimator 27.The 3rd rubbing characteristics estimator 56, the 4th rubbing characteristics estimator 57 use approximate expression 5,6 described later are distinguished computing differential value.Multiplier 59 sum-product intergrators 60 are arranged between totalizer 28 and operating lag compensation section 29.

Each differential value that totalizer 28 calculates the 3rd rubbing characteristics estimator 56, the 4th rubbing characteristics estimator 57 carries out additive operation and outputs to multiplier 59.The rate signal that the differential value that multiplier 59 is exported totalizer 28 and differentiator 22 are exported multiplies each other to calculate the rate of change of friction torque with respect to the time.Integrator 60 is connected with the output terminal of multiplier 59.The rate of change that integrator 60 calculates multiplier 59 carries out time integral computing.Operating lag compensation section 29 is connected with the output terminal of integrator 60.

Operating lag compensation section 29 is made up of the inverse function of transport function.Transport function obtains the characteristic model of the torque from torque instruction signal to motor 2 actual outputs.Torque instruction signal is input to current control amplifier 15 (with reference to Fig. 2).The integrated value that operating lag compensation section 29 is exported integrator 60 is carried out multiplying and is generated friciton compensation signal.

Pairing approximation formula 5,6 describes.The 3rd rubbing characteristics estimator 56, the 4th rubbing characteristics estimator 57 are used approximate expression 5,6.The definition of the various parameters in this variation is identical when above-mentioned approximate expression 1,2 is defined.

Approximate expression the 5, the 6th, differentiates and obtains by x ' pairing approximation formula 1,2.The formula (7) of approximate expression 5 for obtaining after formula (1) being differentiated with x '.

·df ₁/dx’＝2f _c0/a ₀{1-tanh ²(|x’|/a ₀)}+1/a ₁(2f _c1+f _c2-f _c0){1-tanh ²(|x’|/a ₁)}…(7)

The formula (8) of approximate expression 6 for obtaining after formula (2) being differentiated with x '.

·df ₂/dx’＝f _c2/a ₂{1-tanh ²{(|x’|-b)/a ₂}}...(8)

Be located at | x ' | in the situation of-b < 0, df ₂/ dx '=0.

Investigate the difference on effect in the situation that the situation of utilizing the friciton compensation device 13 of above-mentioned embodiment to carry out friciton compensation and the friciton compensation device 106 that utilizes this variation carried out friciton compensation.The former mode is compensation way 1, and the latter's mode is compensation way 2.In Figure 21, represent the data of compensation way 1 with fine rule, represent the data of compensation way 2 with thick line.

Investigate the error of having carried out the friciton compensation in the situation of arc operation and situation to have carried out at a high speed arc operation with non-high speed.As shown in figure 21, carried out circular arc cutting with non-high speed in the situation that, the friction torque while having carried out friciton compensation by compensation way 1,2 is identical.As shown in figure 22, in the situation that having carried out circular arc cutting with high speed, the friction torque while having carried out friciton compensation by compensation way 2 has produced error with respect to compensation way 1.The in the situation that of compensation way 2, obtain for the time being friction torque with respect to the rate of change of time, and the result of obtaining is carried out to time integral computing.Therefore, in the time of high speed, cannot ignore integral error.

As mentioned above, in the time that the control mode of Japanese Patent Publication No. 210273 communiques in 2008 is changed to have carried out the compensation same with the present invention, in the time of non-high speed, can obtain same effect.Mode of the present invention is following mode: utilize the friction estimator that the function with reversal distance shows merely to calculate, and carry out additive operation with torque instruction.The present invention can carry out the friciton compensation from low-speed region to high-speed region accurately, and the present invention is more good compared with mode in the past.

In the above-described embodiment, the formula (1) using in approximate expression 1 is the combination of two groups of tanh functions.Formula (4) is the combination of two groups of exp functions.Section 1 is that tanh function and Section 2 are that the combination of exp function and Section 1 are that exp function and Section 2 are that the combination of tanh function also can obtain same effect.

In the above-described embodiment, the Section 1 of approximate expression 1 is to utilize tanh function or exp function that the friction sharply after reversing is changed and is similar to.Friction sharply after reversion changes after sharply rising and becomes immediately steady state value.Therefore, the Section 1 of approximate expression 1 also can be similar to ramp function or step function.

Above-mentioned embodiment is taking worktable 3 as moving body.Moving body can be also the mechanism of supporting for the main shaft of grasping tool.Stationary work-table in advance.Mechanism also can be made up of main tapping and column.With the mode supporting spindle head that can rotate around the spindle.The mode supporting spindle head of column can make main tapping up and down or move forward and backward.

Use formula (1) is as approximate expression 1, and use formula (5) builds example 7 as approximate expression 2.Use formula (4) is as approximate expression 1, and use formula (2) builds example 8 as approximate expression 2.

In example 7, f _c0=0.9, a ₀=0.0025, f _c1=0.45, a ₁=0.031, f _c2=0.35, a ₂=0.014, b=0.075.In example 8, f _c0=0.9, a ₀=0.00025, f _c1=0.45, a ₁=0.031, f _c2=0.35, a ₂=0.014, b=0.075.Figure 23 is the figure of example 7.Figure 24 is the figure of example 8.

In the present invention, can use any formula in formula (1), (4) these two formulas as approximate expression 1, any formula in use formula (2), (5), (6) these three formulas is as approximate expression 2.Therefore, can be combined into six kinds of methods.

Above-mentioned embodiment has used the feed mechanism of double nut precompressed mode.The present invention also can obtain same effect for the feed mechanism of skew precompressed mode.The feed mechanism of skew precompressed mode forms as one to be configured to a nut by a pair of nuts and washers.The present invention also can obtain same result in the feed mechanism of skew precompressed mode.

Claims (7)

1. a numerical control device, possesses: feed mechanism, and it has ballscrew shaft and the ball nut of fit on this ballscrew shaft, for the moving body being fixed on this ball nut is moved; Motor, it is rotated driving to above-mentioned ballscrew shaft; Position detecting mechanism, its detection utilizes the position of the moving body that above-mentioned motor moves; Speed generating unit, the consistent speed command of position command that its generation makes the position of the detected moving body of this position detecting mechanism generate with control part; Speed detecting mechanism, it detects the speed of above-mentioned motor; Torque generating unit, the consistent torque instruction of speed command that its generation makes the detected speed of above-mentioned speed detecting mechanism generate with above-mentioned speed generating unit; Friction estimator, it estimates the friction force or the friction torque that after the sense of rotation reversion of above-mentioned motor, produce; And correction unit, friction force or friction torque that it estimates according to above-mentioned friction estimator are proofreaied and correct above-mentioned torque instruction,

Wherein, above-mentioned ball nut is made up of a pair of ball nut with multiple balls,

This numerical control device also possesses:

Actual position estimation portion, it estimates the physical location of the above-mentioned moving body corresponding with above-mentioned position command; And

Calculating part, its physical location estimating according to above-mentioned actual position estimation portion calculates the displacement after the moving direction reversion of above-mentioned moving body,

The first friction estimator, it estimates the friction force being caused by above-mentioned feed mechanism or the friction torque of increase from the moving direction reversion of above-mentioned moving body by the displacement that calculates taking above-mentioned calculating part as the approximate expression of variable; And

The second friction estimator, it has moved after ormal weight the friction force or the friction torque that increase due to above-mentioned ballscrew shaft and a pair of ball nut by the displacement that calculates taking above-mentioned calculating part above-mentioned moving body after the approximate expression of variable is estimated the moving direction reversion of above-mentioned moving body

Afore mentioned rules amount is that after the moving direction reversion of above-mentioned moving body, above-mentioned moving body moves in above-mentioned multiple ball distance when at least one ball contacts with above-mentioned a pair of ball nut and 3 of above-mentioned ballscrew shafts,

Above-mentioned friction estimator is carried out additive operation to above-mentioned the first friction estimator and above-mentioned the second friction estimator friction force or friction torque of estimating respectively.

2. numerical control device according to claim 1, is characterized in that,

If the amount of movement that the friction force changing from the moving direction reversion of above-mentioned moving body or friction torque are reversed after moving direction with respect to above-mentioned moving body resolves into the second slope composition that the first slope composition and slope are less than this first slope composition, and the displacement from moving direction backward position of above-mentioned moving body is made as to x ', friction force or the friction torque of the rising from reversion of above-mentioned the first slope composition are made as to f _c0, the rising distance constant of above-mentioned the first slope composition is made as to a ₀, the rising distance constant of above-mentioned the second slope composition is made as to a ₁, the kinetic force of friction changing from the moving direction reversion of above-mentioned moving body or the total value of kinetic friction torque are made as to f _c1, be made as f by having moved the kinetic force of friction being caused by ballscrew shaft and a pair of ball nut or the kinetic friction torque that increase after afore mentioned rules amount after the moving direction reversion of above-mentioned moving body _c2, afore mentioned rules amount is made as to b, be made as a by moved the friction force that increases after afore mentioned rules amount b or the rising distance constant of friction torque from the moving direction reversion of above-mentioned moving body ₂, sign function is made as to sgn, the above-mentioned approximate expression f of above-mentioned the first friction estimator ₁the above-mentioned approximate expression f of (x '), above-mentioned the second friction estimator ₂(x ') be

$f_1\left(x^{\&prime;}\right)=f_{c0}(\tanh \left(\frac{\left|x^{\&prime;}\right|}{a_0}\right)-\frac{1}{2})\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)+(f_{c1}+\frac{f_{c2}}{2}-\frac{f_{c0}}{2})(2\tanh \left(\frac{\left|x^{\&prime;}\right|}{a_1}\right)-1)\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

$f_2\left(x^{\&prime;}\right)=f_{c2}(\tanh \left(\frac{\left|x^{\&prime;}\right|-b}{a_2}\right)-\frac{1}{2})\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

$\left|x^{\&prime;}\right|-b<0\&DoubleRightArrow;f_2\left(x^{\&prime;}\right)=-\frac{f_{c2}}{2}\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right).$

3. numerical control device according to claim 1, is characterized in that,

If the amount of movement that the friction force changing from the moving direction reversion of above-mentioned moving body or friction torque are reversed after moving direction with respect to above-mentioned moving body resolves into the second slope composition that the first slope composition and slope are less than this first slope composition, and the displacement from moving direction backward position of above-mentioned moving body is made as to x ', friction force or the friction torque of the rising from reversion of above-mentioned the first slope composition are made as to f _c0, the rising distance constant of above-mentioned the first slope composition is made as to a ₀, the rising distance constant of above-mentioned the second slope composition is made as to a ₁, the kinetic force of friction changing from the moving direction reversion of above-mentioned moving body or the total value of kinetic friction torque are made as to f _c1, be made as f by having moved the kinetic force of friction being caused by ballscrew shaft and a pair of ball nut or the kinetic friction torque that increase after afore mentioned rules amount after the moving direction reversion of above-mentioned moving body _c2, afore mentioned rules amount is made as to b, be made as a by moved the friction force that increases after afore mentioned rules amount b or the rising distance constant of friction torque from the moving direction reversion of above-mentioned moving body ₂, sign function is made as to sgn, the above-mentioned approximate expression f of above-mentioned the first friction estimator ₁the above-mentioned approximate expression f of (x '), above-mentioned the second friction estimator ₂(x ') be

$f_1\left(x^{\&prime;}\right)=f_{c0}(\frac{1}{2}-\exp \frac{-\left|x^{\&prime;}\right|}{a_0})\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)+(f_{c1}+\frac{f_{c2}}{2}-\frac{f_{c0}}{2})(1-2\exp \frac{-\left|x^{\&prime;}\right|}{a_1})\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

$f_2\left(x^{\&prime;}\right)=f_{c2}(\frac{1}{2}-\exp \frac{-\left(\right|x^{\&prime;}|-b)}{a_2})\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

$\left|x^{\&prime;}\right|-b<0\&DoubleRightArrow;f_2\left(x^{\&prime;}\right)=-\frac{f_{c2}}{2}\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right).$

4. numerical control device according to claim 1, is characterized in that,

If the amount of movement that the friction force changing from the moving direction reversion of above-mentioned moving body or friction torque are reversed after moving direction with respect to above-mentioned moving body resolves into the second slope composition that the first slope composition and slope are less than this first slope composition, and the displacement from moving direction backward position of above-mentioned moving body is made as to x ', friction force or the friction torque of the rising from reversion of above-mentioned the first slope composition are made as to f _c0, the rising distance constant of above-mentioned the first slope composition is made as to a ₀, the rising distance constant of above-mentioned the second slope composition is made as to a ₁, the kinetic force of friction changing from the moving direction reversion of above-mentioned moving body or the total value of kinetic friction torque are made as to f _c1, be made as f by having moved the kinetic force of friction being caused by ballscrew shaft and a pair of ball nut or the kinetic friction torque that increase after afore mentioned rules amount after the moving direction reversion of above-mentioned moving body _c2, afore mentioned rules amount is made as to b, be made as a by moved the friction force that increases after afore mentioned rules amount b or the rising distance constant of friction torque from the moving direction reversion of above-mentioned moving body ₂, sign function is made as to sgn, the above-mentioned approximate expression f of above-mentioned the first friction estimator ₁the above-mentioned approximate expression f of (x '), above-mentioned the second friction estimator ₂(x ') be

$f_1\left(x^{\&prime;}\right)=f_{c0}(\tanh \left(\frac{\left|x^{\&prime;}\right|}{a_0}\right)-\frac{1}{2})\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)+(f_{c1}+\frac{f_{c2}}{2}-\frac{f_{c0}}{2})(2\tanh \left(\frac{\left|x^{\&prime;}\right|}{a_1}\right)-1)\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

$f_2\left(x^{\&prime;}\right)=f_{c2}(\frac{1}{2}-\exp \frac{-\left(\right|x^{\&prime;}|-b)}{a_2})\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

$\left|x^{\&prime;}\right|-b<0\&DoubleRightArrow;f_2\left(x^{\&prime;}\right)=-\frac{f_{c2}}{2}\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right).$

5. numerical control device according to claim 1, is characterized in that,

If the amount of movement that the friction force changing from the moving direction reversion of above-mentioned moving body or friction torque are reversed after moving direction with respect to above-mentioned moving body resolves into the second slope composition that the first slope composition and slope are less than this first slope composition, and the displacement from moving direction backward position of above-mentioned moving body is made as to x ', friction force or the friction torque of the rising from reversion of above-mentioned the first slope composition are made as to f _c0, the rising distance constant of above-mentioned the first slope composition is made as to a ₀, the rising distance constant of above-mentioned the second slope composition is made as to a ₁, the kinetic force of friction changing from the moving direction reversion of above-mentioned moving body or the total value of kinetic friction torque are made as to f _c1, be made as f by having moved the kinetic force of friction being caused by ballscrew shaft and a pair of ball nut or the kinetic friction torque that increase after afore mentioned rules amount after the moving direction reversion of above-mentioned moving body _c2, afore mentioned rules amount is made as to b, be made as a by moved the friction force that increases after afore mentioned rules amount b or the rising distance constant of friction torque from the moving direction reversion of above-mentioned moving body ₂, sign function is made as to sgn, the above-mentioned approximate expression f of above-mentioned the first friction estimator ₁the above-mentioned approximate expression f of (x '), above-mentioned the second friction estimator ₂(x ') be

$f_1\left(x^{\&prime;}\right)=f_{c0}(\frac{1}{2}-\exp \frac{-\left|x^{\&prime;}\right|}{a_0})\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)+(f_{c1}+\frac{f_{c2}}{2}-\frac{f_{c0}}{2})(1-2\exp \frac{-\left|x^{\&prime;}\right|}{a_1})\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

$f_2\left(x^{\&prime;}\right)=f_{c2}(\tanh \left(\frac{\left|x^{\&prime;}\right|-b}{a_2}\right)-\frac{1}{2})\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

$\left|x^{\&prime;}\right|-b<0\&DoubleRightArrow;f_2\left(x^{\&prime;}\right)=-\frac{f_{c2}}{2}\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right).$

6. numerical control device according to claim 1, is characterized in that,

If the displacement from moving direction backward position of above-mentioned moving body is made as to x ', be made as f by having moved the kinetic force of friction being caused by ballscrew shaft and a pair of ball nut or the kinetic friction torque that increase after afore mentioned rules amount after the moving direction reversion of above-mentioned moving body _c2, afore mentioned rules amount is made as to b, be made as a by moved the friction force that increases after afore mentioned rules amount b or the rising distance constant of friction torque from the moving direction reversion of above-mentioned moving body ₂, sign function is made as to sgn, the above-mentioned approximate expression f of above-mentioned the second friction estimator ₂(x ') be

$f_2\left(x^{\&prime;}\right)=-\frac{f_{c2}}{2}\cos \left(\frac{\left|x^{\&prime;}\right|-b}{a_2}\mathrm{\&pi;}\right)\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right)$

$\left|x^{\&prime;}\right|-b<0\mathrm{or}\left|x^{\&prime;}\right|-b-a_2>0\&DoubleRightArrow;f_2\left(x^{\&prime;}\right)=-\frac{f_{c2}}{2}\mathrm{sgn}\left(\frac{{\mathrm{dx}}^{\&prime;}}{\mathrm{dt}}\right).$

7. a friciton compensation method, comprise the following operation of being undertaken by the numerical control device that possesses feed mechanism, motor and position detecting mechanism: speed generates operation, generate the consistent speed command of position command that the position of the detected moving body of above-mentioned position detecting mechanism is generated with control part; Speed detects operation, detects the speed of above-mentioned motor; Torque generates operation, generates and makes above-mentioned speed detect the consistent torque instruction of speed command that the detected speed of operation generates with above-mentioned speed generation operation; Operation is estimated in friction, estimates the friction force or the friction torque that after the sense of rotation reversion of above-mentioned motor, produce; And correcting process, the friction force or the friction torque that estimate according to above-mentioned friction estimation operation are proofreaied and correct above-mentioned torque instruction, wherein, above-mentioned feed mechanism has ballscrew shaft and the ball nut of fit on this ballscrew shaft, for the moving body being fixed on this ball nut is moved, above-mentioned motor is rotated driving to above-mentioned ballscrew shaft, and above-mentioned position detecting mechanism detects the position that utilizes the moving body that above-mentioned motor moves

Wherein, above-mentioned ball nut is made up of a pair of ball nut with multiple balls,

This friciton compensation method also comprises:

Actual position estimation operation, it estimates the physical location of the above-mentioned moving body corresponding with above-mentioned position command; And

Calculation process, its physical location estimating according to above-mentioned actual position estimation operation calculates the displacement after the moving direction reversion of above-mentioned moving body,

Operation is estimated in the first friction, estimates the friction force being caused by above-mentioned feed mechanism or the friction torque of increase from the moving direction reversion of above-mentioned moving body by the displacement that calculates taking above-mentioned calculation process as the approximate expression of variable; And

Operation is estimated in the second friction, the friction force or the friction torque that increase due to above-mentioned ballscrew shaft and a pair of ball nut have been moved after ormal weight by the displacement that calculates taking above-mentioned calculation process above-mentioned moving body after the approximate expression of variable is estimated the moving direction reversion of above-mentioned moving body

Afore mentioned rules amount is that after the moving direction reversion of above-mentioned moving body, above-mentioned moving body moves in above-mentioned multiple ball distance when at least one ball contacts with above-mentioned a pair of ball nut and 3 of above-mentioned ballscrew shafts,

Estimate in operation in above-mentioned friction, above-mentioned the first friction is estimated to operation and above-mentioned the second friction estimate that friction force or friction torque that operation estimates respectively carry out additive operation.