JPH07104725B2 - Manipulator drive system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Object of the Invention [Field of Industrial Application] The present invention relates to a driving system for a manipulator.

As for the type of manipulator operation method, first, in the case of industrial robots, which are a type of manipulator, especially for painting robots, welding robots, sealing robots, etc., the operator works by holding the gun at the end of the arm. Is often taught.

Further, in a master-slave type manipulator used when an operator in an operation environment remote from the work environment performs an actual work in the work environment, the operator moves the master side arm by hand to reduce the work environment. Operate the slave arm to perform the work.

Furthermore, when handling a heavy object with a manipulator, an operation is performed in which the manipulator holds the heavy object and the operator puts his or her hand on it to control the manipulator so as to move the heavy object along the movement of the operator's hand. A method can be considered.

In the above three manipulator operating methods, it is necessary that the arm moves along the movement of the operator faithfully, and it is possible to assist the force that the operator bears 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] These manipulators are controlled so that they faithfully transmit the movements of the operator, ensure the safety of the operator, and assist the force that the operator bears. However, in order to drive, it is basically necessary to detect the external force acting on the manipulator.

Conventionally, a force sensor is used to detect an external force acting on the manipulator. However, in principle, the force sensor has an advantage that the force can be easily detected, but it has many errors, its operation is unstable, the measured values vary, and it is expensive. Moreover, when the number of joint axes increases, the force detection mechanism becomes complicated. Further, since the sensor is generally placed at the tip of the arm, it is not possible to detect interference or collision at the middle part of the arm. Under such circumstances, the development of countermeasure technology is desired.

The present invention has been made in view of the above circumstances and can easily and accurately detect an external force acting on a manipulator, and apparently reduces the load and the weight of the manipulator to zero, and greatly reduces the inertial force / friction force. It is an object of the present invention to provide a manipulator drive system that can assist the force borne by the operator by reducing the number of the manipulators, and that has a simple structure and is inexpensive.

(B) Configuration of the Invention [Means for Solving the Problem] To this end, the drive system of the manipulator according to the present invention is a low-speed drive provided at the joint of the arm of the manipulator.
In a joint direct drive type manipulator driven by using a high-torque motor, a motor current detector that detects a current of the motor, a potentiometer that detects a joint angle of the shaft of the joint, and a joint angular velocity of the shaft of the joint A tachogenerator for detecting the output of the tachogenerator, a tachogenerator signal differentiator for differentiating the output signal of the tachogenerator, and a servo amplifier, and the motor current by the motor current detector, the joint angle by the potentiometer, and the joint angular velocity by the tachogenerator. The external force acting on the arm is derived from the joint angular acceleration by the tacho-generator signal differentiator, and the signal resulting from canceling the force due to the potential is amplified by the servo amplifier and input to the motor.

Hereinafter, details of the present invention will be described with reference to the drawings illustrating an embodiment.

In FIG. 1, 1 is a manipulator, and an operator 2
To operate. In the manipulator 1, one or a plurality of arms 3 are connected by one or a plurality of joints 4 so as to be capable of relative displacement. The operator 2 bears the load 5 when operating the manipulator 1. The arm 3 is driven by a motor 6 built in the joint 4. That is, the 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.

The control device is shown in FIG. The controller 7 includes a motor current detector 8, a potentiometer 11, a tacho generator 12, a tacho generator signal differentiator 13, and a servo amplifier 14.
And an external force torque detection circuit 15.

The motor current detector 8 detects the current of the motor 6 and inputs it to the 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 differentiates the output of the tacho-generator 12 to derive the joint angular acceleration of the axis of the joint 4 and inputs it to the external force torque detection circuit 15. External torque detection circuit 15
Derives the external force torque acting on the joint 4 from the motor current by the motor current detector 8, the joint angle by the potentiometer 11, the joint angular velocity by the tachogenerator 12, and the joint angular acceleration by the tachogenerator signal differentiator 13. 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. Servo amplifier 14
The signal amplified by and canceling the force due to the potential is input to the motor 6, and the arm 3 is driven.

[Operation] In a manipulator of a direct joint drive system that uses a low-speed and high-torque motor, nonlinear friction, backlash, spring component, etc. are extremely small. Therefore, the arm motion equation is J: arm inertia moment and load moment, b : Viscous friction coefficient, K: Motor constant τ ₀ : External force torque, τ _g (θ): Potential torque, θ: Rotation angle, i: Motor current, G: External force amplification factor Is represented.

The left side first term is obtained from the output of the motor current detector 8, the left side third term is determined from the potentiometer 11 output, the right side second term is determined from the tacho generator 12 output, and the right side first term is determined from the tacho generator signal differentiator 13 output. Therefore, the external force of the second term on the left side can be obtained.

τ ₀ = J + b−Ki−τ _g (θ) The external force signal τ ₀ thus obtained is multiplied by the amplification factor G, and the potential term τ _g (θ) is removed, and the motor current i to be generated by the servo amplifier is If i = (Gτ ₀ −τ _g (θ)) / K, the motion of the manipulator is (1 + G) τ ₀ = J + b. The potential τ _g (θ) is canceled out, resulting in a state in which the load and the weight of the arm are zero, and the amplified torque Gτ ₀ acts in addition to the original external force τ ₀ , and the external force Since the effect is amplified by (1 + G) times, external force (operating force) can be assisted.

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

In the control device 7b, for each joint axis, the servo amplifier 14,
The motor 6, the potentiometer 11, and the tacho-generator 12 are provided, and the external force torque detection circuit of the control device 7 of FIG.
A computer 16 is used in place of 15, the input side of the computer 16 is connected to a servo amplifier 14, a motor 6, a potentiometer 11, a tacho generator 12, and a tacho generator signal differentiator 13 via an A / D converter 17, and Output side is D / A
Each servo amplifier 14 is connected via a converter 18.

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

For the 1st axis when the number of axes is n, the equation of motion of the arm is Next to The external force τ _0l can be _calculated by (C) Effect of the invention In the driving method of the manipulator of the present invention, no special force sensor is used, and the motor, tachometer and potentiometer which are conventionally provided in each joint of the manipulator are used. Since the external force can be detected by using as it is, it is not necessary to change the sensor configuration of the conventional manipulator, and the external force can be detected inexpensively with a simple structure.

Moreover, since the force sensor is not used, the operation is extremely stable without the problems of environment resistance and noise resistance due to the physical characteristics of the force sensor.

In addition, the apparent weight of the load is zero by assisting the operating force,
The inertial mass and viscous friction can be apparently set to 1 / (g + 1) (g: feedback gain), and the manipulator can be operated by the operator with an extremely small force.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a manipulator, FIG. 2 is a configuration explanatory diagram of a control device when there is one joint (1 axis), and FIG. 3 is a configuration explanation of a control device when there are multiple joints (multi-axis). FIG. 4 and FIG. 4 are explanatory views 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 torque detection circuit, 16 …… Computer, 17 …… A / D converter, 18…
… D / A converter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-59-189416 (JP, A) JP-A-59-176805 (JP, A) JP-A-59-107882 (JP, A) JP-A-59- 157715 (JP, A)

Claims (1)

[Claims] 1. A manipulator of a direct joint drive system, which is driven by using a low-speed / high-torque motor provided in a joint of an arm of a manipulator, and a motor current detector for detecting a current of the motor, and a shaft of the joint. A potentiometer for detecting a joint angle, a tacho-generator for detecting a joint angular velocity of the axis of the joint, a tacho-generator signal differentiator for differentiating an output signal of the tacho-generator, and a servo amplifier are provided. From the motor current, the joint angle by the potentiometer, the joint angular velocity by the tacho-generator, and the joint angular acceleration by the tacho-generator signal differentiator, an external force acting on the arm is derived and a signal that cancels the force by the potential is used to generate the servo signal. Amplify with an amplifier and input to the motor Drive system of the manipulator, characterized