JPH0392287A - Performance evaluation method for manipulator - Google Patents

Abstract

PURPOSE:To evaluate, with high precision, vibration and the shift of a track at the tip of a robot manipulator, by seeking a shift quantity and a function which is of a parallel advance direction displacement, conducting the least square approximation by an (n) function, and evaluating the quantity of the shift of the track. CONSTITUTION:A movable plane is pressed against a contacter 6 to restrict the free parallel advance 2 direction of the contacter 6 so that the detection value of a force detector 5 may become a set value. The movable plane is fixed at a time point on which this detection value has become the set value, and then, a robot manipulator 1 tip is made to make an uniform velocity linear movement in an unrestricted parallel advance direction. The detection value of the force detector 5 at this movement process is read. A shift quantity D from a linear track at this instance is sought from the detection value of the force detector 5. The quantity of the shift of the track is evaluated by conducting the approximation of a vibration center value locus which is expressed with the relation of this shift quantity D and the parallel direction displacement Py, by an (n) function.

Description

[Detailed Description of the Invention] [Summary] Concerning a performance evaluation method for robot manipulators that evaluates vibrations and trajectory deviations at the tip of a manipulator, the vibrations and trajectory deviations of the tip of a manipulator can be evaluated with high precision without the use of special equipment. For the purpose of evaluation, a contact is attached to the tip of the manipulator via a force detector, and the movable plane is set so that the detected value of the force detector becomes the set value in order to constrain the contact in two arbitrary translational directions. When the detected value of the force detector reaches the set value, fix the movable plane, and after fixing the movable plane, move the tip of the maniplate unrestrained in one translational direction at a constant velocity. Move linearly, read the detected value of the force detector during the process of uniform linear movement, calculate the amount of deviation ΔD from the linear trajectory from the detected value from the force detector, and calculate the amount of deviation ΔD and the displacement in the translational direction. The trajectory of the center value of vibration expressed from the relationship is approximated by an n-th order function to evaluate the deviation of the trajectory. Further, the amplitude and frequency characteristics of the vibration are determined using the approximate value of the center value locus and the deviation amount ΔD.

[Industrial application field]

The present invention relates to a performance evaluation method for a robot manipulator that evaluates vibrations, trajectory deviations, etc. at the tip of the robot manipulator.

[Conventional technology]

Robot manibrator (hereinafter referred to as manipulator)
When performing assembly work using a , it is desirable to accurately follow a given trajectory. Therefore, it is important to understand the trajectory tracking performance of the manibrake used in factory automation.

[Problem to be solved by the invention]

By the way, the vibration of the tip of the mani plate is several 10 to several 10
This often occurs on the order of 0 um, and simply observing the absolute position in space with a camera or the like does not have enough resolution to capture the vibration, which is a problem.

The present invention was created in view of this point, and the deviation from the trajectory when a straight trajectory is commanded to the manibrake (i.e., the difference between the coordinate system held inside the manibrake and the reference coordinate system provided in the environment) The purpose of the present invention is to provide a performance evaluation method for robot manipulators that can evaluate with high precision the vibrations generated at the tip (misalignment) and the vibration generated at the tip.

[Means to solve the problem]

FIG. 1 is a diagram explaining the principle of the present invention. As shown in the figure, there are two directions of translation of the tip of the manipulator 1 (for example, X.
,Z. ) is constrained and made to move uniformly in one unconstrained translation direction (YR). At this time, vibrations occurring in the direction of the constraint degree of freedom of the manipulator generate contact force with the constraint surface. Therefore, a contact probe 6 is attached to the tip of the manipulator l via a force sensor 5. The force sensor 5 itself generally has an analog output, but an A/D converter (not shown)
The resolution can be easily refined by operating the range. A highly rigid plane parallel to two directions (for example, X., Z) of the reference coordinate system (0* A target force f is applied in the XI1 direction between . x+Z
*Target force f in the direction. 2 will occur. Goal power (
The constraint surface is fixed when the set value is reached. Then, with the restrained surface fixed, the unrestricted direction (Y direction)
The maniplate is moved linearly at a speed v0a.

Here, if the tip of the manibrake 1 vibrates or the trajectory deviates from the Y direction, the deviation ΔD from the initial displacement is regarded as forced displacement due to servo control. At this time, the displacement ΔD of the spring of the force sensor 5 becomes equivalent to ΔD by making the restraining surface highly rigid (K.=(X)) (see FIG. 2). Therefore, the spring constant of the force sensor 5 is K
s, and the viscous resistance coefficient is C, then Fu=C, ΔDI +K3ΔD, ...■Δ
D=ΔD3 where t is time, Fu(t)=Fs(t)−Fu,F,
(t) represents the detection force as a function of time, F0 represents the pressing force in the initial state, and a represents Ks/Cs.

If zero or a detected value with a polarity opposite to the target force occurs in Fs during observation, it means that the contact probe 6 has moved away from the restraining surface. Therefore, in such a case, the observation is invalid.

In order to make the observation effective, it is sufficient to increase the pressing force F0 in the initial state and reset the constraint plane. In addition, the deviation Δ
The stiffness of the force sensor 5 needs to be selected to a low value so that the contact force generated by D does not disturb the robustness of the servo of the manibrake 1.

The relationship between ΔD and Py (=Vy t) determined by equation (2) represents the vibration of the tip of the manipulator and the deviation of the trajectory. For example, trajectory deviation (i.e. linearity deviation in the YR direction),
If both tip vibrations exist, the relationship shown in Figure 3 (
(solid line), and in the case of only tip vibration, it is represented by a solid line as shown in FIG. In Figures 3 and 4, (a)
The figure shows the behavior in the x, 1 direction, and the figure (b) shows the behavior in the z, 1 direction.

Based on the above observed values, the following statistical processing is performed as performance evaluation.

(a) Evaluation of trajectory deviation The relationship between ΔD and P is obtained by least square approximation using an n-th order function. That is, the locus Q (Py) of the center value of vibration indicates a trajectory deviation.

(b) Evaluation of tip vibration The dispersion of ΔD regarding the center value locus obtained in (a) is determined assuming a normal distribution (Fig. 5). That is, the standard deviation σ or 3σ of ΔD (p, )−Q (p, ) of all data is used as the evaluation value. ΔD (P, ) represents the observed value at Py, and Q (py) represents the central value at P.

The frequency characteristic of vibration is ΔD (P, ”) −Q (P,
) can be obtained as a frequency spectrum as shown in FIG. 6 by FFT (fast Fourier transform) analysis.

〔Example〕

FIG. 7 is a diagram showing an example of the configuration of a system for implementing the present invention. In the figure, 1 is a manipulator, 2 is a power amplifier, 3 is a D/A converter, 4 is a controller that controls the manipulator, 5 is a force sensor, 6 is a contact probe, 7 and 8 are restraint surfaces, 9 and 10 is a motor, 11 is a power amplifier, 12 is a D/A converter, 13 is a controller for controlling the motor, 14 is an A/D converter, 15 is a signal processing section, 16 is a CRT, and 17 is a keyboard.

The manibrator 1 is a known industrial robot provided in combination with a power amplifier 2, a D/A converter 3, and a controller 4.

A contact probe 6 is attached to the tip of the manibrator 1 via a force sensor 5, and the force sensor 5 detects the contact force between the restraining surfaces 7 and 8.

The detected voltage is converted into a digital signal by the A/D converter 14, and the signal processing section 15 calculates ΔD.

When the motor 9 is rotated, the ball screw rotates, thereby moving the restraint surface 7 from side to side. Similarly, motor 1
When 0 is rotated, the ball screw rotates, which causes the restraint surface 8 to move up and down. A command signal output from the controller 13 is sent to the motors 9 and 10 via the two-axis D/A converter 12 and the two-axis power amplifier 11. The controller 13 controls the motor 9.10 until an initial pressing force F0 is generated.

FIG. 8 is a diagram showing an example of the structure of the restraining surface. In the same figure, 18 and 19 are restraint surfaces, 20 and 21 are motors, and 22 and 2
3 indicates a guide rail, and 24 and 25 indicate ball screws, respectively.

When the motor 20 rotates, the ball screw 25 also rotates,
This causes the restraining surface l8 to slide.

Similarly, rotating the motor 21 causes the ball screw 24 to rotate, thereby causing the restraint surface 19 to slide.

FIG. 9 is a diagram showing the processing of each part in the embodiment of FIG. 7. In this example, it is assumed that the x, I, and Z directions are constrained, and the trajectory tracking performance of the X, Z, and I directions with respect to movement in the Y and Y directions is observed.

Therefore, when using the restraint surface with the structure shown in Fig. 8,
It is installed so that the restraining surface 18 is perpendicular to X8. In the initial posture of the manipulator, the axis of the force sensor 5 is the reference coordinate system (
OR XR YR ZR) is set by operating the controller 4 independently. The symbols in the figure have the following meanings.

Fo: Target pressing force in the initial state (f.ll+f.. in the wooden example) V0: Target value of movement speed in the unrestrained direction (V.y in this example) L: Distance in the unrestrained direction (in this example, V.y) In this example, 1y) F, two-force detection value (in this example, f.., f..) t: Measurement time ΔD: Observable amount (in this example, ΔdX+ Δd.) In addition, the thin arrows in the same figure indicate the respective constituent elements. The thick arrows indicate communication between certain elements via a bus.

If you want to observe the orbit, press Fo,
V. , L. Then, the controller 13 and the signal processing section 15 are activated.

The controller l3 performs the following processing.

■ Store Fo, Vo, and L in RAM.

■ Read F from the RAM of the signal processing unit 15. ■
Force control of restraint surfaces.

■ Check whether Fu=Fs. If Yes, proceed to ■; if No, return to ■.

■ Finish controlling the restraint surface and fix it.

■ Turn on the initial state setting completion flag.

■V. , L to the controller 4. The controller 4 controls the maniplate 1 according to the given V0, L.

Furthermore, when activated, the signal processing unit 15 performs the following processing.

■’V. , L in RAM.

■' Sample the signal from the A/D converter 14.

■ Calibrate (calculate Fs).

■"F" is stored in RAM.

■ Check whether the initial state setting end flag is on. Y
If es, proceed to ■“, and if No, return to ■゜.

■゜Start the timer. The initial value is O.

■”■Calculate according to the formula.

(2) Check whether IF, is 0 or has the opposite polarity to F0.

If yes, proceed to @゛; if NO, proceed to ■゛.

■ Store V@Xt vs. ΔD in RAM.

[Phase]' Check whether t=r,/vo. If Yes, proceed to ■゛; if No, return to ■“.

``Perform the evaluation process shown in FIG. 10.

@’　Display “observation is invalid” on CRT.

FIG. 10 is a diagram showing the flow of evaluation processing. First, ΔD
The relationship between

Next, σ or 3σ of ΔD (p, )−Q (p, ) is calculated, and σ or 3σ is displayed in the format shown in FIG.

Finally, ΔD (P, )−Q (P, ) is subjected to FFT analysis, and the peak frequency is displayed in the format shown in FIG.

(Effects of the Invention) As is clear from the above description, according to the present invention, vibration and trajectory deviation at the tip of a robot manipulator can be evaluated with high accuracy without using any special equipment.

[Brief explanation of drawings]

Fig. 1 is a diagram illustrating the principle of the present invention, Fig. 2 is a diagram illustrating the contact state, Fig. 3 is a diagram illustrating the vibration and trajectory deviation of the tip of the manipulator, and Fig. 4 is a diagram showing the vibration of the tip of the manipulator. , Fig. 5 is a diagram explaining the evaluation of tip vibration, Fig. 6 is a diagram showing the frequency characteristics of vibration, Fig. 7 is a diagram illustrating an example of the system configuration for implementing the present invention, and Fig. 8 is a diagram showing the structure of the system for implementing the present invention. FIG. 9 is a diagram showing an example of the structure of a surface, FIG. 9 is a diagram showing processing of each part of the embodiment, and FIG. 10 is a diagram showing the flow of evaluation processing. 1... Manibrake, 2... Power amplifier, 3...
... D/A converter, 4... Controller that controls the manipulator, 5... Force sensor, 6... Contact probe, 7 and 8... Restraint surface, 9 and 10... Motor,
11...Power amplifier, 12...D/A converter, l3...Controller for controlling motor, etc., 1
4... A/D converter, 15... Signal processing section, 1
6...CRT, 17...Keyboard.

Claims (1)

[Claims] (1) A contact (6) is attached to the tip of the robot manipulator (1) via a force detector (5), and the contact (6) is movable to restrain any two translational directions (X_R, Z_R). Press the plane against the contact (6) so that the detected value of the force detector (5) becomes the set value, and fix the movable plane when the detected value of the force detector (5) reaches the set value. , After fixing the movable plane, the robot manipulator (1
) in an unrestrained translation direction (Y_R), read the detected value of the force detector (5) in the process of uniform linear movement, and calculate the deviation ΔD from the linear trajectory at this time. From the detected value of the force detector (5), ΔD=e^-^a^t{1/C_s∫F_u(t)e^
a＾tdt} (where a is a constant determined by the force detector (6), t is time, F_u(t) = F_s(t) - F_
0, F_s(t) is the detected value as a time function, and F_0 is the pressing force in the initial state). A performance evaluation method for a robot manipulator characterized by approximating the trajectory of the center value of vibration by an n-th order function to evaluate the amount of trajectory deviation.