JPS62119610A - Drive control device for arm having tactual sense - Google Patents

Abstract

PURPOSE:To get in contact with an object with a prescribed force without the intervention of a processor by switching automatically a position or speed command control for a drive control of a hand into a force command control when a hand or a contact is in contact with the object at a scheduled force. CONSTITUTION:A switch circuit 13 switching outputs of the 1st control circuit 11 generating a position of speed differential output the 2nd control circuit 12 generating a force differential output is provided, and when a force applied to an end effector exceeds a command value, the switch circuit 13 is thrown to the position of the 2nd control circuit 12 so as to drive an arm A coupled with said end effector via a plate spring S by the force control. Since the force command control is constituted by analog circuits, the response speed is fast and the processing by a processor is not required.

Description

[Detailed Description of the Invention] [Summary] A switch circuit is provided that switches and outputs the output of a first control circuit that generates a position or velocity differential output and a second control circuit that generates a force differential output, and an end effector. When the force applied to the end effector exceeds a command value, the switch circuit is switched to the second control circuit so that the arm connected to the end effector by the leaf spring is driven by force control.

[Industrial application field]

In a surface profiling device or a robot, it is necessary to bring an end effector equipped with a contactor or a hand close to a target object and to contact the target object with a predetermined force.

To achieve such a function, it is necessary to perform position control or speed control to bring the end effector closer to the target object, but it is also necessary to control only the position or speed after contacting the target object. If this continues, the object may be pushed around, or in extreme cases, the object may be destroyed. Therefore, a robot was developed that has the ability to sense when it comes into contact with an object.

[Conventional technology and its problems]

The arm and end effector (robot hand,
Hooke's law F = kx (here, F force, k is the stiffness of the elastic body, and X is the deflection of the elastic body) It is common to detect force by

In conventional devices of this type, a predetermined force was controlled by controlling the deflection of the elastic body using, for example, a 50 μm pitch stepping function. It is difficult to apply this method to control robots used on manufacturing lines because it cannot follow the robot's position and moves slowly, and it also has the disadvantage of increasing the burden on the processor because it relies on position control. .

[Means for solving problems]

The present invention automatically switches the drive control of the hand from position or speed command control to force command control when the hand or contactor contacts a target object with a predetermined force, thereby achieving a predetermined control without the need for processor intervention. It is designed so that it can contact the target object with the force of .

Since the force command control can be configured by an analog circuit, the response speed is fast, and since processing by a processor is not required, the drawbacks of the above-mentioned prior art can be eliminated.

〔Example〕

FIG. 1 shows an embodiment of the present invention, in which it is applied to control of a profiling device for automatically measuring the shape of a curved surface.

The profiling device (MM) has an arm (A) that moves vertically by a worm shaft (W) driven by a motor (M) fixed to a base (B), and two pieces on this arm (A). The end effector (E) is connected via a leaf spring (S) and has a degree of freedom in the vertical direction, and is equipped with a contact (P) that contacts the object to be measured. Tracing is performed by bringing the contacts into contact with force.

In order to detect this contact force, one of the leaf springs (S) installed between the arm (A) and the end effector (E) is equipped with a strain gauge (S G ) for detecting the amount of deflection of this spring. ) is attached to the rotating shaft of the motor (M) to detect the moving speed of the arm (A), and a position coder (PE) to detect the position of the arm. It is equipped with

Figure 2 shows a robot hand in which the end effector (E) is equipped with a finger for gripping an object, a motor (HM) for opening and closing the finger, and an angle encoder (HE) for detecting the degree of opening and closing of the finger (F). The present invention can be applied in the same way as the tracing device shown in FIG.

The first control circuit (11) is a circuit that controls the position or movement speed of the end effector (E), and receives a speed command or position command from the processor (10), and the vertical movement speed of the arm (A). from the coucometer (T) attached to the shaft of the motor (M), and from the arm (A).
) are feed-hacked from the position coder (PE).

The second control circuit (12) receives a force command from the processor (10), and calculates the amount of deflection of the leaf spring (S) detected by the strain gauge (SG), that is, the end effector (I?,). The contact pressure of the object to be measured is feedhacked via a switch control circuit (20) to be described later.

These first. The output of the second control circuit (i], 12) is an analog switch (13) whose switching is controlled by the output of the switch control circuit (20), and a power amplifier (14).
Drive power is supplied to the motor (M) through.

When the switch (13) is on the first control circuit (11) side, the first control circuit (11) is connected to the processor (10).
The difference between the position command from the tachometer and the displacement amount from the position encoder, or the difference between the speed command from the processor and the motor rotation speed from the tachometer is detected and the difference is applied to the motor (M). A normal feedback control system is configured to match the displacement amount or speed to a standard value from the processor (1()).

Now, when a command is issued from the puller 1-1 processor (10) to lower the arm by, for example, 30 m, the arm (A) and therefore the end effector (E) start lowering, and the contactor (P) is Since the leaf spring (S) is in contact with the object to be measured, the leaf spring (S) is deflected, and the strain gauge (SG) produces an output proportional to the contact pressure of the contact.

This output converts the offset command value from the processor (10) that determines the contact pressure into the digital-to-analog exchanger (21).
), this analog signal is subtracted from the output of the strain gauge (SG) by a subtracter (22), and this difference signal is fed back to the second control circuit (12) to issue a force command. On the other hand, the comparator (23) compares the output from the strain gauge (S'G) proportional to the amount of deflection of the spring (S) with the output of the digital-to-analog converter (21), so that the output of the strain gauge is When the offset value from the processor is exceeded, the analog switch is switched to the second control circuit (1
2) produces an output that switches so that the output of 2) is supplied to the power amplifier.

However, in cases where the end effector (E) moves and stops due to vibrations caused by inertia, or when the end effector is equipped with a gripping mechanism and used as a robot and pushes an object, force control is performed using the output of the strain gauge. If you do so, a malfunction will occur, so the processor (10
) sends a switch enable signal from gate -(2
4, ) is shut off, and the analog switch (13) is held on the first control circuit (11) side to continue supplying the speed or position control signal from the first control circuit to the motor.

As described above, in the present invention, when the output of the strain gauge (SG) exceeds the offset value from the processor, the force control is automatically performed. It is okay to continue to release
Further, if only the force command value and offset value are output, there is no need to perform any processing, so that the negative (■) of the processor can be reduced.

However, if the second control circuit 11Pr (12) is configured to simply increase the difference between the command value of the processor and the value obtained by subtracting the offset value from the output of the strain gauge, stable control cannot be performed.

FIG. 3 shows an equivalent circuit when the embodiment shown in FIG. 1 performs force control, Ap is the second control circuit (1
2) is the gain due to the operational term intermediater and the power amplifier (14), and this output is applied to the DC motor (M), and the electrical characteristics of the motor (M) are as shown in 102. The output current is 1 (s ) is generated, and this current multiplied by the motor's force constant (current-mechanical force conversion constant) Kf represents the mechanical output of the motor.

The force of the mechanical output of this motor to move the object is the arm (A)
Since a spring (S) is interposed between the and the contact (P), the repulsive force proportional to the amount of movement (deflection) of this spring (S) is subtracted, and this becomes the force of the moving object (Fig. 1). For example, the end effector (E), the probe (P), etc., and the end effector (E) as shown in Figure 2.
When the robot is used as a robot with a gripping device, the robot also includes the gripping device and the object being gripped. ) is the product of the quality EIM and the Laplace operator S, plus the viscous braking constant (braking force that occurs as the moving speed increases) D. The reciprocal of the value is the velocity of the moving object, and the integral value of this is the velocity of the moving object. Since the amount of movement is , force control becomes possible by performing a feedbank that matches the force command from the processor (10), that is, the amount of movement due to the slack of the spring (S).

At this time, the amount of deflection X (s) of the spring (S) in response to the force command F(S) from the processor (10) is given by the following equation.

...(1) The electrical constant L/R of a DC motor is generally L/R (1, so if the numerator and denominator are divided by R/R and L/R'=O, then the above equation (1) can be approximated as follows.

Xl5) ApKf k+
/RFls) MS” + (D+XeK
f/R)S +K +ApKfkl/R...(2) In this equation (2), the condition that the spring (S) does not cause vibration is as follows, and the right side of this equation (3) is the response of the control system. The natural frequency ω indicates The larger this value is, the better the responsiveness will be. If the equality holds, for example, when you hit it, it will immediately return and stop, and if the inequality holds, it will wrinkle and return to its original position after you hit it. It is preferable to operate as close to the condition that the sign holds as possible.

Therefore, if we look at equation (3), we can see that 1 is included as a value that can be adjusted in a particular system, so by rewriting equation (3), we can obtain the following equation for kl. .

Z ... (4) A in the published version of this formula includes the open loop gain of the operational term intermediater in the second control circuit, and normally reaches 120 db, or 1 million digits, but the denominator is The value of is a tens-digit value, and the right side is substantially equal to O, which is virtually impossible to realize.In other words, it can be seen that the system shown in FIG. 1 is a system that is prone to vibration.

Therefore, as shown in Fig. 4, a differentiator S is added to differentiate the moving distance of the end effector (E), multiplied by a constant k2, and this is subtracted from the output of 1 to the term middle unit to obtain the operational term. When it returns to the input of the intermediate device, the amount of deflection X (s) of the leaf spring (S) in response to the force command F (s) at this time is expressed as , as described above, and as described above, L / R<<
1, the approximate expression of equation (5) is i! i, X(SI K f Ap k
1F (sl MS20 (04-KeKf
/ R+ Ap Kfkz/R) S+ (K ten hep
Kfk+/R)...(6) Formula is obtained. Here, the quadratic term of S in the right-hand side denominator represents the viscosity, and the -th term represents the responsiveness, and as the value of the quadratic term increases, the viscosity increases, and the -th term represents the responsiveness. As the value of the term increases, the responsiveness increases, and these values can be changed by 2 and +, respectively.

If we find the conditions under which the parallel spring (S) does not vibrate using this equation in the same way as equation (3), we get...(7), and in order to satisfy this equation (7), 1 and 2 are By determining the response and viscosity, stable control can be performed by selecting the response and viscosity. Incidentally, if only kl is increased to improve the responsiveness, vibrations are likely to occur, so it is necessary to increase 2 to 1 to reduce the difference between the values on both sides.

Generally, a desirable condition is to make both sides of equation (7) equal, and even for the above-mentioned changes in the stationary mass M and constant kl, the following value where both sides of equation (7) are equal: 2Mω, .

A stable control system can be obtained by choosing 2 for kl so as to keep it constant.

FIG. 5 shows a specific example of the second control circuit (■2) to which the differentiator (D) as described above is added.
The analog command value obtained by converting the force command value from the resistor (32
), the output of the strain gauge (SG) is connected to the subtraction input via a resistor (33), and the output is fed back to the subtraction input via a resistor (34). 35), and the strain gauge (SG) output is connected to a capacitor (36) and a resistor (3
7) and connect it to the subtraction input terminal,
It is equipped with a differentiator (D) consisting of an operational amplifier (39) which is fed back from the output side to the subtraction input terminal via a resistor (38), and the differential amplifier (A) and the differentiator are The outputs are added by resistors (40, 41) and output to an output arithmetic amplifier (
42) and the analog switch (1
3) is configured to be output to the fixed terminal.

According to this specific example, if the gain of the differential amplifier (A) is 3
3 and the value of the resistor 34, and this gain corresponds to the above gain of 1, and the gain of the differentiator (D) is determined by the ratio of the value of the resistor 34.
7 and the value of the resistor 38, and this gain corresponds to the above gain of 2, so these resistors 33, 34,
By adjusting the value of 37.38, the responsiveness and viscosity of the system can be optimized.

Therefore, if the circuit shown in FIG. 5 is applied to the second control circuit of the embodiment shown in FIG. 1, more stable control can be performed.

Above, we explained about one degree of freedom, but two-dimensional or three-dimensional
When controlling the “transition of dimensions”, [these control systems are
It is clear that an iJ system or three systems would be sufficient.

〔Effect of the invention〕

According to the present invention, the processor automatically switches between position control, speed control, and force control simply by outputting a command value, and since force control is performed by analog control, the response speed is fast. , and the burden on the processor is reduced.

Moreover, if the circuit shown in FIG. 5 is applied to the second control circuit, even more stable control can be performed.

[Brief explanation of drawings]

Figure 1 is an example of the present invention, Figure 2 is an example of application to a robot, Figure 3 is an equivalent circuit for force control, Figure 4 is an equivalent circuit for improved force control, and Figure 5 is an improved example. A specific example of the second control circuit is shown below.

Claims (2)

[Claims] (1) An end effector (E) connected to an arm (A) driven by a drive source (M) via a leaf spring (S).
), and means (T) for detecting the moving speed of the arm (A).
), means (PE) for detecting the position of this arm (A), and means (SG) for detecting the deflection of the leaf spring (S). , a first control circuit (11) that compares the position command value or speed command value from the processor (10) with the output of the position detecting means (PE) or the moving speed detecting means (T) and generates a differential output; , the subtractor (22) subtracts the offset value from the processor (10) from the output of the leaf spring deflection detecting means (SG) and supplies the subtracted output to the second control circuit; a switch control circuit (20) that outputs the output of a comparator circuit (23) that generates an output when the output exceeds the offset value via a gate (24) that opens and closes in response to a switch enable signal from the processor;
), a second control circuit (12) that generates a difference output between the subtraction output supplied from the switch control circuit (20) and the force command value from the processor (10), and the first control circuit (11). ) and the second control circuit (
12) and an analog switch (13) that outputs the output by switching the output of the gate (24) of the switch control circuit (20), and amplifying the output of the analog switch (13) 1. A drive control device for an arm having a tactile sense, characterized in that the drive control device is configured to supply power to a drive source (M) of a tactile sense. (2) The second control circuit (12) is connected to the switch control circuit (2).
0) and a force command value from the processor (10).
33, 34), a differentiating circuit (D) including gain control means (37, 38) in parallel with this circuit, and this differential amplifier (A). and differential circuit (D)
2. The drive control device according to claim 1, further comprising means (40, 41) for adding the outputs of.