CN102636366A - Operation performance evaluation method of machine tool feed system based on torque signal of motor - Google Patents

Abstract

The invention relates to an operation performance evaluation method of a machine tool feed system based on a torque signal of a motor. The operation performance evaluation method comprises the following steps of: getting an output torque signal and a position signal of a servomotor during the no-load constant-speed whole feed travel by utilizing a communication interface of an open type numerical control system, segmenting the torque signal according to the feed position and taking a peak-to-peak value of an instant impact component during commutation between feed and return as a transient stability characteristic; fitting a trend function of the torque signal in a smooth feed area relative to the feed position by a least square method as a structure performance characteristic of the feed system; taking the peak-to-peak value, the frequency spectrum peak value and the frequency value corresponding to the frequency spectrum peak value of the remaining short-term fluctuation signal as operation performance characteristics; and comparing the three types of the characteristics and evaluating the operation performances of different numerical control machine tool feed systems. According to the operation performance evaluation method disclosed by the invention, the quantitative detection and the comparative evaluation of the operation performance of the feed system can be realized, and the method further has important significance for ensuring the processing efficiency and the feed precision of a numerical control machine tool.

Description

A kind of machine tool feed system performance appraisal procedure based on motor torque signal

Technical field

The invention belongs to numerically-controlled machine dynamic property detection technique, be specifically related to a kind of machine tool feed system performance appraisal procedure based on motor torque signal.

Background technology

Numerically-controlled machine is the basic production equipment in the processing and manufacturing field, has increasingly automated and characteristics mechanical electronic hydraulic integrated.The service check of numerically-controlled machine comprises that mainly geometric accuracy is measured and runnability detects two aspects at present; Geometric accuracy is measured and is called the static accuracy check again; Be used to detect line face shape error and position displacement error after parts are assembled, the moving situation of key mechanism such as the feeding when the runnability detection then is used for assessing machine tool running, main shaft.The detection of runnability and assessment not only reflect the coordination and the mated condition of each component movement of lathe, also embody the optimization of matching degree of physical construction and control system, and be significant to the working (machining) efficiency and the precision that guarantee numerically-controlled machine.

Feed system is to keep the machine cut campaign to continue the system ensemble of carrying out, because the compact sealing of its space structure is in the continuous motion, and work under bad environment, the installation and the use of external sensors such as vibration, temperature, displacement receive great restriction.Therefore, utilize digital control system in open type, gather and handle displacement, speed and servomotor torque data that built-in sensor (grating chi, scrambler, motor current sensor etc.) provides, become the new technical means that the feed system runnability detects gradually.Yet in the feeding process; The motion of mechanical part receives the servocontrol of position and speed; Operation is detected to be under the condition of work complicated and changeable; The real-time adjustment information of runnability information and control loop is aliasing in the detection signal, under the situation of effectively not separating, is difficult to set up reliable runnability evaluation index.

Summary of the invention

In order to overcome the shortcoming of above-mentioned prior art; The object of the present invention is to provide a kind of machine tool feed system performance appraisal procedure based on motor torque signal; The drive motor dtc signal that provides with the built-in sensor of digital control system is an analytic target; Extract through signal decomposition and characteristic index, in the full feed distance scope of unloaded constant speed, realize the quantitative evaluation of runnability.

To achieve these goals, the technical solution taked of the present invention is:

A kind of machine tool feed system performance appraisal procedure based on motor torque signal; Servomotor output torque with the full feed distance of unloaded constant speed; Be decomposed into temporary impact, trend function and short period fluctuation; Extract the characteristic index of reflection feed system transient stability, structural behaviour and exercise performance respectively, realize the runnability assessment of feed system, may further comprise the steps:

1), gathers the supplying position signal P (t in the unloaded constant speed total travel of the feed shaft two-way process through the communication interface of digital control system in open type _i) and drive motor dtc signal T (t _i), t wherein _iBe sampling instant;

2) according to supplying position signal P (t _i), find out the initial moment and the t finish time in astable feeding stage _BAnd t _E, the astable feeding stage comprises startup, switching-over or becomes the level stage, with t _B≤t _i≤t _EDrive motor dtc signal in time period is temporary impact composition T _I, i.e. T _I=T (t _i), t _B≤t _i≤t calculates feeding and comes and goes the temporary impact composition peak-to-peak value max (T when commutating _I)-min (T _I), with it as feed system transient stability characteristic;

3) use least square fitting to stablize the trend function of drive motor dtc signal and supplying position in the feeding district, this trend function select usually straight-line equation T ' (t)=a+bP (t), wherein $b=\frac{n\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}P\left(t_i\right)T\left(t_i\right)\right]-\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}P\left(t_i\right)\right]\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}T\left(t_i\right)\right]}{n\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}P{\left(t_i\right)}^2\right]-{\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}P\left(t_i\right)\right]}^{\text{2}}},$ $a=\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}T\left(t_i\right)-b\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}P\left(t_i\right),$ t ₁Be the initial moment of meadow, t _nBe that the meadow stops constantly, n is a steady feeding district sampling number, with the absolute value of the straight-line equation slope b structural behaviour characteristic as feed system;

4) from the drive motor dtc signal, deduct temporary impact composition and trend function, obtain short period fluctuation signal T _F, the peak-to-peak value max (T of calculating short-term fluctuation signal _F)-min (T _F), and obtain the spectrogram of short-term fluctuation signal through Fourier transform, with peak-to-peak value, spectrum peak, spectrum peak respective frequencies value as the exercise performance characteristic;

5) the runnability eigenwert of the different NC machine tool feed system of contrast; The more for a short time feed system transient stability that shows of temporary impact composition peak-to-peak value is good more when coming and going switching-over; The more for a short time feed system structural behaviour that shows of trend function slope value is good more; Fluctuating short period, peak-to-peak value is more for a short time to show that the torque of feed system overall friction is more little, and exercise performance is good more, and short period fluctuation spectrum peak indicates the consumed energy and the motion frequency of main friction acting parts.

Runnability appraisal procedure provided by the invention has not only been avoided installation external sensor, and efficiently solves servo-controlled interference problem, for the detection of NC machine tool feed system runnability and evaluation provide new thinking, has following characteristics:

1. the control feed system is moved under unloaded constant speed condition, has eliminated the influence that cutting moment and motor speed change, and makes drive motor output torque equal the friction torque that mechanical part causes, has guaranteed the rationality of analytic target.

2. utilize the processing monitoring and the data communication facility of digital control system in open type, obtain supplying position signal and drive motor dtc signal in the feeding total travel two-way process, method is simple, and data are reliable.

3. from the drive motor dtc signal, extract the characteristic index of transient stability, structural behaviour and exercise performance, realize the comprehensive Quantified Evaluation of runnability.

4. the feed system of different numerically-controlled machines can be carried out runnability and laterally contrasted, for precision and the reliability that improves feed system provides foundation.

Description of drawings

Fig. 1 is the signal analysis process flow diagram of feed system runnability appraisal procedure of the present invention.

Fig. 2 is the hardware composition diagram of embodiment of the invention signals collecting.

Fig. 3 is the cnc boring and milling machine feed system synoptic diagram of the embodiment of the invention.

Fig. 4 is that the X of milling-boring machine 1 is to unloaded total travel supplying position signal of feed system and drive motor dtc signal figure.

Fig. 5 is that the X of milling-boring machine 1 is to the unloaded feeding total travel of feed system drive motor dtc signal exploded view.

Fig. 6 is that the X of milling-boring machine 2 is to unloaded total travel supplying position signal of feed system and drive motor dtc signal figure.

Fig. 7 is that the X of milling-boring machine 2 is to the unloaded feeding total travel of feed system drive motor dtc signal exploded view.

Embodiment

Do the present invention is further specified below in conjunction with accompanying drawing and embodiment.

With reference to shown in Figure 1, a kind of machine tool feed system performance appraisal procedure based on motor torque signal may further comprise the steps:

1), gathers the supplying position signal P (t in the unloaded constant speed total travel of the feed shaft two-way process through the communication interface of digital control system in open type _i) and drive motor dtc signal T (t _i), t wherein _iBe sampling instant;

2) according to supplying position signal P (t _i), find out the initial moment and the t finish time in astable feeding stage _BAnd t _E, the astable feeding stage comprises startup, switching-over or becomes the level stage, with t _B≤t _i≤t _EDrive motor dtc signal in time period is temporary impact composition T _I, i.e. T _I=T (t _i), t _B≤t _i≤t calculates feeding and comes and goes the temporary impact composition peak-to-peak value max (T when commutating _I)-min (T _I), with it as feed system transient stability characteristic;

3) use least square fitting to stablize the trend function of drive motor dtc signal and supplying position in the feeding district, this trend function select usually straight-line equation T ' (t)=a+bP (t), wherein $b=\frac{n\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}P\left(t_i\right)T\left(t_i\right)\right]-\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}P\left(t_i\right)\right]\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}T\left(t_i\right)\right]}{n\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}P{\left(t_i\right)}^2\right]-{\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}P\left(t_i\right)\right]}^{\text{2}}},$ $a=\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}T\left(t_i\right)-b\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}P\left(t_i\right),$ t ₁Be the initial moment of meadow, t _nBe that the meadow stops constantly, n is a steady feeding district sampling number, with the absolute value of the straight-line equation slope b structural behaviour characteristic as feed system;

4) from the drive motor dtc signal, deduct temporary impact composition and trend function, obtain short period fluctuation signal T _F, the peak-to-peak value max (T of calculating short-term fluctuation signal _F)-min (T _F), and obtain the spectrogram of short-term fluctuation signal through Fourier transform, with peak-to-peak value, spectrum peak, spectrum peak respective frequencies value as the exercise performance characteristic;

5) the runnability eigenwert of the different NC machine tool feed system of contrast; The more for a short time feed system transient stability that shows of temporary impact composition peak-to-peak value is good more when coming and going switching-over; The more for a short time feed system structural behaviour that shows of trend function slope value is good more; Fluctuating short period, peak-to-peak value is more for a short time to show that the torque of feed system overall friction is more little, and exercise performance is good more, and short period fluctuation spectrum peak indicates the consumed energy and the motion frequency of main friction acting parts.

With reference to shown in Figure 2; The hardware of signals collecting of the present invention is formed and is comprised: machine tool feed system, digital control system, multi-point communication cable, address card and notebook computer; Embodiment selects Siemens 840D digital control system, and corresponding address card model is CP5512, and SF is about 13Hz.

With reference to shown in Figure 3; The embodiment of the invention is selected certain large-scale high-grade digital-control boring-milling machine; Adopt column to move the console mode layout that the main spindle box side is hung; Can accomplish the motion of five kinds of straight-line feeds: column moves laterally that (X to), main spindle box vertical moving (Y to), ram move axially that (Z to), boring axle move axially (W to) and turntable vertically moves (V to), and turntable gyration (B to).Embodiment is that object launches the exercise performance analysis and assessment with X to feed system.

With reference to shown in Figure 4, milling-boring machine 1 is gathered supplying position signal P (t) and the drive motor dtc signal T (t) of X in the unloaded total travel of feed system.Its X is the spur gear rack structure to feeding, and the gear number of teeth is 38, and modulus is 6, and total travel is 6000mm, reference position coordinate-2500mm, final position coordinate-8500mm, speed of feed 5000mm/min.

With reference to shown in Figure 5, the X of milling-boring machine 1 is decomposed into temporary impact, trend function and short period fluctuation to feed system drive motor dtc signal.X to the feed system enable position is-2500mm; Commutation position is-8500mm that stop position is-2500mm to extract the temporary impact composition of above-mentioned three positions; Wherein commutation position impact maximum, with its peak-to-peak value 23.79Nm as this feed system transient stability characteristic; Use least square fitting to remove the trend function of drive motor dtc signal and supplying position in the stable feeding district of startup, switching-over and stop position, wherein just the stroke trend function be T ' (t)=-1.59+3.09 * 10 ^-5P (t), the revesal trend function be T ' (t)=-7.12+1.63 * 10 ^-4P (t) is with slope absolute value 3.09 * 10 ^-5With 1.63 * 10 ^-4Structural behaviour characteristic as this feed system; From the drive motor dtc signal, deduct temporary impact composition and trend function, obtain the short-term fluctuation signal, its peak-to-peak value is 12.26Nm; Frequency peak is 2.53; Crest frequency is 0.116Hz, and as the runnability characteristic, the corresponding X of crest frequency 0.116Hz is to stroke 718.39mm; Be approximately equal to pitch circle girth 716mm, show that main friction acting produces by spur gear is eccentric.

With reference to shown in Figure 6, milling-boring machine 2 is gathered supplying position signal P (t) and the drive motor dtc signal T (t) of X in the unloaded total travel of feed system.Its X is a spiral gear tooth bar structure to feeding, and the gear number of teeth is 52, and modulus is 4.5, and total travel is 5500mm, reference position coordinate 500mm, final position coordinate 6000mm, speed of feed 5000mm/min.

With reference to shown in Figure 7, the X of milling-boring machine 2 is decomposed into temporary impact, trend function and short period fluctuation to feed system drive motor dtc signal.X is 500mm to the feed system enable position, and commutation position is 5500mm, and stop position is 500mm, extracts the temporary impact composition of above-mentioned three positions, wherein commutation position impact maximum, with its peak-to-peak value 17.35Nm as this feed system transient stability characteristic; Use least square fitting to remove the trend function of drive motor dtc signal and supplying position in the stable feeding district of startup, switching-over and stop position, wherein just the stroke trend function be T ' (t)=0.89+6.81 * 10 ^-5P (t), the revesal trend function be T ' (t)=9.09-7.74 * 10 ^-5P (t) is with slope absolute value 6.81 * 10 ^-5With 7.74 * 10 ^-5Structural behaviour characteristic as this feed system; From the drive motor dtc signal, deduct temporary impact composition and trend function, obtain the short-term fluctuation signal, its peak-to-peak value is 3.58Nm, and frequency peak is 0.64, and crest frequency is 0.102Hz, as the runnability characteristic.The corresponding X of crest frequency 0.102Hz is approximately equal to tooth bar length 820mm to stroke 816.99mm, shows that main friction acting is produced by the engagement of spiral gear tooth bar.

As shown in table 1, two lathe X are decomposed to feed system drive motor dtc signal, extract and remove the various features index.

Table 1:

Can know by table 1; Milling-boring machine 2-X all is better than milling-boring machine 1-X to feed system to feed system each item index; Transient stability is good, and forward and reverse operating structure performance is consistent, and the mechanical part frictional dissipation is little; This conclusion is consistent with actual conditions, satisfies the requirement of NC machine tool feed system runnability quantitative evaluation.

Claims (1)

1. machine tool feed system performance appraisal procedure based on motor torque signal; It is characterized in that; Servomotor output torque with the full feed distance of unloaded constant speed is decomposed into temporary impact, trend function and short period fluctuation, extracts the characteristic index of reflection feed system transient stability, structural behaviour and exercise performance respectively; Realize the runnability assessment of feed system, may further comprise the steps:

1), gathers the supplying position signal P (t in the unloaded constant speed total travel of the feed shaft two-way process through the communication interface of digital control system in open type _i) and drive motor dtc signal T (t _i), t wherein _iBe sampling instant;

2) according to supplying position signal P (t _i), find out the initial moment and the t finish time in astable feeding stage _BAnd t _E, the astable feeding stage comprises startup, switching-over or becomes the level stage, with t _B≤t _i≤t _EDrive motor dtc signal in time period is temporary impact composition T _I, promptly _TI=T (t _i), t _B≤t _i≤t calculates feeding and comes and goes the temporary impact composition peak-to-peak value max (T when commutating _I)-min (T _I), with it as feed system transient stability characteristic;

3) use least square fitting to stablize the trend function of drive motor dtc signal and supplying position in the feeding district, this trend function select usually straight-line equation T ' (t)=a+bP (t), wherein $b=\frac{n\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}P\left(t_i\right)T\left(t_i\right)\right]-\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}P\left(t_i\right)\right]\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}T\left(t_i\right)\right]}{n\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}P{\left(t_i\right)}^2\right]-{\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}P\left(t_i\right)\right]}^{\text{2}}},$ $a=\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}T\left(t_i\right)-b\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\Σ}}}P\left(t_i\right),$ t ₁Be the initial moment of meadow, t _nBe that the meadow stops constantly, n is a steady feeding district sampling number, with the absolute value of the straight-line equation slope b structural behaviour characteristic as feed system;

4) from the drive motor dtc signal, deduct temporary impact composition and trend function, obtain short period fluctuation signal T _F, the peak-to-peak value max (T of calculating short-term fluctuation signal _F)-min (T _F), and obtain the spectrogram of short-term fluctuation signal through Fourier transform, with peak-to-peak value, spectrum peak, spectrum peak respective frequencies value as the exercise performance characteristic;

5) the runnability eigenwert of the different NC machine tool feed system of contrast; The more for a short time feed system transient stability that shows of temporary impact composition peak-to-peak value is good more when coming and going switching-over; The more for a short time feed system structural behaviour that shows of trend function slope value is good more; Fluctuating short period, peak-to-peak value is more for a short time to show that the torque of feed system overall friction is more little, and exercise performance is good more, and short period fluctuation spectrum peak indicates the consumed energy and the motion frequency of main friction acting parts.

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