JPH06182682A - Speed control method for robot - Google Patents

Abstract

PURPOSE:To simply and accurately determine the speed command of a robot during acceleration or deceleration. CONSTITUTION:An ideal acceleration/deceleration data table indicating the ideal acceleration/deceleration curve in the data table is stored in a wave-form generating memory 6. A CPU 1 reads the data table at the time of acceleration or deceleration, determines the speed command at each time via the scaling (expansion or shrinkage) of the data table in response to the speed difference and the acceleration/deceleration time, and moves an actuator 5 in response to this speed command.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control method for robots, and is applied to robots, manipulators, machine tools, transportation machines and the like.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIG. The CPU 1 shown in the figure calculates a command signal for the actuator 5 based on the speed command stored in the memory 2 and outputs it to the D / A converter 3. The memory 2 holds the position command and speed command of the actuator 5. The D / A converter 3 is
The speed command from the CPU 1 is D / A converted and transmitted to the speed command generation circuit 4 for the actuator 5. The speed command generation circuit 4 converts the output of the D / A converter 3 as necessary for driving the actuator 5. The actuator 5 is C
A robot axis (not shown) is driven according to a command from PU1.

In the prior art having the above structure, when the robot is driven by reproduction or the like, the CPU 1 calculates the speed according to the contents of the memory 2, and the result is passed through the D / A converter 3 and the speed command generation circuit 4. To drive the actuator 5.

[0004]

In robot control, speed control during acceleration / deceleration is a major factor in determining smoothness of movement, rod life, and the like.

[0005] In the conventional speed control, as shown in FIG. 6, when attempting to acceleration and deceleration from the speed V ₁ to velocity V _2, the rate between the velocity V ₁ ~ speed V _2, the Ya delay of the mechanical system In consideration of overshoot and the like, a multi-dimensional curve such as an S-shaped curve is used and divided at every minute sampling time Δts as shown in FIG. 7, and the velocities V _t and V ′ _t at the times t and t + Δts.
Is calculated and converted into a discrete pseudo curve.

Therefore, in order to smoothly perform the acceleration / deceleration operation, the sampling time Δts can be reduced, and it depends on bringing the discrete pseudo curve close to the theoretical curve. However, in the conventional technique, while operating, Δ
Since the solution of the multidimensional curve is calculated for each ts, if the degree of the curve is high, the calculation load of the CPU 1 becomes very heavy. Therefore, the required calculation time is more than the sampling time Δts,
As a result, the number of speed calculation points in the acceleration / deceleration time becomes smaller and the order of the curve decreases, which enters a vicious circle, and there is a problem that the use of a higher-order curve does not have the expected effect.

In view of the above-mentioned conventional technique, it is an object of the present invention to provide a robot speed control method capable of reducing the calculation load on the CPU and improving the motion trajectory accuracy.

[0008]

In order to solve the above problems, according to the present invention, when a velocity value during robot acceleration / deceleration is calculated, an acceleration / deceleration curve is converted into a data table in advance and held in a memory to solve the curve. The feature is that the calculation is performed only by scaling the data table stored value without obtaining it.

[0009]

In the present invention, when controlling the acceleration / deceleration of the robot,
The CPU generates a speed command in which the acceleration / deceleration curve stored in the waveform generation memory is added to the speed command stored in the memory, and drives the actuator via the D / A converter and the speed command generation circuit.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. It should be noted that parts having the same functions as those of the conventional technique are designated by the same reference numerals, and redundant description will be omitted.

FIG. 1 shows an embodiment of the present invention. In the present embodiment, the waveform generation memory 6 holds the data (FIG. 3B) obtained by converting the ideal acceleration / deceleration curve shown in FIG. 3A into a data table. The CPU 1 calculates the speed during acceleration / deceleration from the speed command held in the memory 2 and the acceleration / deceleration curve data table held in the speed generation memory 6.

Next, the operation will be described with reference to the schematic flow chart shown in FIG.

During acceleration / deceleration of the robot, the CPU 1 has a memory 2
Then, the current speed V ₁ , the next target speed V ₂ , and the acceleration / deceleration time ta are read (step S1).

The CPU 1 reads the ideal acceleration / deceleration curve data table (FIG. 3B) from the waveform generation memory 6 (step S2). In the waveform generation memory 6, an ideal acceleration / deceleration curve data table obtained by converting the ideal acceleration / deceleration curve (FIG. 3 (a)) optimal for the machine into N data and converting it into a data table (FIG. 3 (b)) in advance. keeping.

The CPU 1 applies the scaling coefficient a _{t in} the time direction and the scaling coefficient a _{v in the} speed direction to the actual acceleration / deceleration state (FIG. 6), respectively, using equations (1),
Calculation is performed according to (2) (step S3). However, N is the number of discrete sampling data, and L is the acceleration / deceleration time. a _t = N / t _a Equation (1) _av = (V ₁ −V ₂ ) L Equation (2)

The CPU 1 calculates the data position i on the reference speed curve data table at the time t from the time t (FIG. 6) and the number of data N in the data table (FIG. 3 (b)) by the equation (3). i = t × a _t Equation (3)

The CPU 1 uses the data DT (i) (FIG. 3 (b)) on the data table designated by the data position i and the velocity direction scaling coefficient a _v to change the velocity ΔV _t (FIG. 3 (c)) is arithmetically output (step S4). ΔV _t = a _V × DT (i) (4)

From ΔV _{t of} the equation (4) and the current velocity V ₁ , the velocity V _c at the time t is calculated and output by the equation (5). V _t = V ₁ + ΔV _t (5)

The operations from steps S1 to S5 are repeated until the next target speed V ₂ is reached. (Step S5).

[0020]

According to the present invention, the following effects can be obtained.

By preparing the optimum acceleration / deceleration multidimensional curve as a data table for the speed calculation during acceleration / deceleration of the robot, the data table can be referred and expanded without calculating the solution of the multidimensional curve during operation. , The calculation load of the CPU can be greatly reduced because it can be obtained only by reduction.

As a result, the sampling time during curve interpolation can be shortened as compared with the conventional case, the discrete pseudo curve at the time of acceleration / deceleration can be made closer to the theoretical curve, and the motion of the machine becomes smoother. The accuracy is improved and the life of the machine is also improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart showing the procedure of the embodiment.

FIG. 3 is a characteristic diagram showing an ideal acceleration / deceleration curve, an ideal acceleration / deceleration curve data table, and scaling data.

FIG. 4 is a waveform diagram showing an actual output.

FIG. 5 is a block diagram showing a conventional technique.

FIG. 6 is a characteristic diagram showing ideal acceleration / deceleration control.

FIG. 7 is a characteristic diagram showing acceleration / deceleration control by conventional calculation.

[Explanation of symbols]

 1 CPU 2 Memory 3 D / A Converter 4 Speed Command Generation Circuit 5 Actuator 6 Waveform Generation Memory

Claims (1)

[Claims] 1. A speed control method for a robot, which performs acceleration / deceleration of a robot according to an ideal acceleration / deceleration curve, stores an ideal acceleration / deceleration curve data table in which the ideal acceleration / deceleration curve is converted into a data table, and stores the acceleration / deceleration. The ideal acceleration / deceleration curve data table is sometimes referred to, and the data table is scaled according to the speed difference and the acceleration / deceleration time to obtain the speed at each time during acceleration / deceleration and output it as a speed command. Robot speed control method.