JPS61224012A - Driving system of manipulator - Google Patents

Abstract

PURPOSE:To make it possible to detect external force cheaply using simple constitution by detecting external force using a motor, a tachogenerator and a potentiometer provided in each joint. CONSTITUTION:A motor current detector 8 detects current of a motor and inputs to an external force torque detecting circuit 15. A potentiometer 11 detects joint angle of axis of a joint and inputs to the circuit 15. A tachogenerator 12 detects angular velocity of axis of a joint and inputs to the circuit 15. A tachogenerator signal differentiator 13 differentiates output of the tachogenerator 12 and derives angular acceleration of joint of axis of a joint and inputs to the circuit 15. The circuit 15 derives torque of external force torque acts to the joint form the input. The derived external force torque signal is amplified by a servo amplifier 14. At this time, a signal is given to the amplifier 14 are inputted to a motor 6, and an arm is driven thereby.

Description

Detailed Description of the Invention (a) Purpose of the Invention [Field of Industrial Application] The present invention relates to a drive system for a manipulator.

Regarding the types of manipulator operation methods, first, industrial robots, which are a type of manipulator, especially painting robots, welding robots, sealing robots, etc., are operated by the operator by holding a gun at the end of the arm and moving it. This is often taught.

In addition, in master-slave type manibilators, which are used when the actual work in a work environment is performed by an operator located in an operation environment remote from the work environment, the operator can manually move the mask-side arm to control the work environment. Operate the lower slave side arm to perform the work.

Furthermore, when handling a heavy object with a manipulator, the operator holds the heavy object on the manipulator, puts his hand on it, and controls the manipulator to move the heavy object in accordance with the movement of the operator's hand. There are possible ways.

In the above three manipulator operating methods, it is necessary for the arm to move faithfully along with the operator's movements, and it is necessary to assist the force borne by the operator so that the operator can move the arm with a small force. It is necessary to ensure the safety of the manipulator and the operator.

[Prior Art] The manipulator is controlled in such a way as to faithfully transmit the operator's movements, ensure the safety of the operator, and furthermore, fully and satisfactorily assist the force borne by the operator. However, in order to drive the manipulator, it is basically necessary to detect the external force acting on the manipulator.

Conventionally, force sensors have been used to detect external forces acting on manipulators. In principle, force sensors have the advantage of being able to easily detect force, but they are prone to many errors (i.e., their movements are unstable, resulting in variations in measured values, and they are expensive. When the number of axes increases, the problem is that the force detection mechanism becomes complicated.Also, since the sensor is generally placed at the tip of the arm, it is not possible to detect interference or collisions in the middle of the arm. Development of countermeasure technology is desired.

This invention was made in view of the above-mentioned circumstances, and can easily and accurately detect the external force acting on the manipulator, reducing the apparent load and weight of the manipulator to zero, and greatly reducing inertial force and frictional force. The object of the present invention is to provide a driving type manipulator that can assist the force borne by the operator by reducing the amount of force required by the operator, and that has a simple structure and is inexpensive.

(B) Structure of the Invention [Means for Solving the Problem] In response to this objective, the manipulator drive system of the present invention provides a low-speed
In a joint direct drive type manipulator driven using a high-torque motor, the manipulator includes a motor current detector that detects the current of the motor, a potentiometer that detects the joint angle of the joint axis, and an rJA node of the joint axis. The tacho generator includes a tacho generator that outputs an angular attack velocity, a tacho generator signal differentiator that differentiates an output signal of the tacho generator, and a servo amplifier, and the tacho generator outputs a motor current from the motor current detector, a joint angle from the potentiometer, and a tacho generator from the tacho generator. The external force acting on the arm is derived from the joint angular velocity and the joint angular acceleration by the tacho generator signal differentiator, and the derived external force signal is amplified by the servo amplifier and input to the motor.

Hereinafter, details of the present invention will be explained with reference to the drawings showing one embodiment.

In FIG. 1, 1 is a manipulator, and an operator 2
operates. The manipulator 1 has one or more arms 3 connected by one or more connecting parts 4 so as to be relatively displaceable. The operator 2 bears a load 5 when operating the manipulator 1. The arm 3 is driven by a motor 6 built into the joint 4. That is, a joint direct drive system is adopted. As the motor 6, a motor that does not require a speed reduction mechanism, that is, a low-speed, high-torque direct drive motor is used.

FIG. 2 shows the control device. The control device 7 includes a motor current detector 8, a potentiometer 11, a tacho generator 12, and a tacho generator 0? It is equipped with a signal differentiator 13, a servo amplifier 14, and an external force torque detection circuit 15.

Motor current detector 8 detects the current of motor 6 and inputs it to external force torque detection circuit 15 .

The potentiometer 11 detects the joint angle of the axis of the joint 4 and inputs it to the external force torque detection circuit 15 .

The tacho generator 12 detects the joint angular velocity of the axis of the joint 4 and inputs it to the external force torque detection circuit 15 .

The tacho generator signal differentiator 13 is the tacho generator 1
The joint angular acceleration of the axis of the joint 4 is derived by differentiating the output of 2 and inputted to the external force torque detection circuit 15. The external force torque detection circuit 15 detects the external force torque acting on the joint 4 from the motor current detected by the motor current detector 8, the joint angle detected by the potentiometer 11, the joint angular velocity detected by the tachometer generator 12, and the joint angular acceleration detected by the tachometer signal differentiator 13. Derive. The derived external force torque signal is amplified by the servo amplifier 14. At this time, a signal is given to the servo amplifier 14 so as to cancel the force due to the potential. The signal amplified by the servo amplifier 14 and canceling the potential force is input to the motor 6, and the arm 3 is driven.

[Operation] In a joint direct drive type manipulator using a low-speed, high-torque motor, nonlinear lL! Since friction, backlash, spring components, etc. are extremely small, the equation of motion of the arm is: J: Moment of inertia of arm and load, b: Viscosity @ coefficient of friction, K: Motor constant τ: External force torque, τg (θ): Depends on potential It is expressed as torque, θ: rotation angle, i: motor current, and G gain.

The output of the motor current detector 8 is the first term on the left side, the output of the tensionometer 1 is the third term on the left side, the output of the tacho generator 12 is the second term on the right side, and the output of the tacho generator signal differentiator 13 is the first term on the right side. Therefore, the external force of the second term on the left side can be found.

τo=Jθ+bθ−)(i−τg(θ), and one signal is needed to amplify the external force signal with the servo amplifier.Furthermore, a signal is given to the servo amplifier so as to cancel τ(θ) due to the potential. Then, a state occurs as if the load and the weight of the arm were zero, and the external force (operating force) can be assisted.

[Other Embodiments] Next, FIG. 3 shows the configuration of a control device 7b having a plurality of joints (multi-axis).

The control device 7b has a servo amplifier 1 for each axis of each joint.
4, a motor 6, a potentiometer 1, and a tacho generator 12 are provided, and a computer 16 is used in place of the external force torque detection circuit 15 of the control device @7 in FIG. 2, and the input side of the computer 16 is connected to an A/D converter 17. The servo amplifier 14, the motor 6, the potentiometer 1, the tacho generator 12, and the tacho generator signal differentiator 13 are connected through the servo amplifier 14, and the output side is connected to each servo amplifier 14 through the D/A converter 18. .

FIG. 4 shows an algorithm for the first axis of n axes.

For the first axis when the number of axes is n, the equation of motion of the arm is +b, θ1 a! It becomes a friction term, and the external force τ is Kl'1−τg1(θ). 1 can be found.

(C) Effects of the Invention The manipulator drive method of the present invention does not use a special force sensor, but instead uses the motor, tachogenerator, and potentiometer conventionally provided at each joint of the manipulator to detect external force. Therefore, there is no need to make any changes to the sensor configuration of the conventional manipulator, and external force can be detected at low cost with a simple structure.

Furthermore, since no force sensor is used, the operation is extremely stable without any problems with environmental resistance or noise resistance due to the physical characteristics of the force sensor.

In addition, by assisting the operating force, the load is apparently zero,
Inertial stress, viscosity r! When I saw i rubbing, 1/(Q+1>(Q
:feedback gain), allowing the operator to operate the manipulator with extremely small force.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the manipulator, Figure 2 is an explanatory diagram of the configuration of the control device when there is one joint (single axis), and Figure 3 is the configuration of the control device when there are multiple joints (multi-axis). The explanatory diagram and FIG. 4 are explanatory diagrams showing the algorithm of the control device in the case of multiple axes. 1... Manipulator 2... Operator 3...
・Arm 4...Joint 5...Load 6...
- Motor 7.7b... Control device 8... Motor current detector 11... Potentiometer 12... Tacho generator 13... Tacho generator signal differentiator 14... Servo amplifier 15... External force torque Detection circuit 16... Computer 17... A/
D converter 18...D/A converter Fig. 3 Fig. 4

Claims (1)

[Claims] In a joint direct drive type manipulator that is driven using a low-speed, high-torque motor provided at the joint of a manipulator arm, a motor current detector detects the current of the motor, and a joint angle of the axis of the joint is detected. A potentiometer, a tacho generator for detecting the joint angular velocity of the axis of the joint, a tacho generator signal differentiator for differentiating the output signal of the tacho generator, and a Sardar amplifier, the motor current detected by the motor current detector and the potentiometer The external force acting on the arm is derived from the joint angle by the tachometer, the joint angular velocity by the tacho generator, and the joint angular acceleration by the tachogenerator signal differentiator, and the derived external force signal is amplified by the servo amplifier and applied to the motor. Manipulator drive system characterized by input