JPH05250029A - Industrial robot - Google Patents

Abstract

PURPOSE:To easily execute teaching operations while an operator supports the suitable part of a relevant robot by torque controlling an actuator to apply an operational load to the operator based on a torque signal when an operating condition is switched to a direct teaching mode. CONSTITUTION:When the operating condition is switched from a regenerative operation mode to a direct teaching operation mode by operating a switch box 1 by the operator, based on an angle signal from an angle detector 7 and the torque signal from a torque detector 6, a motor 5 is torque controlled by a controller 8 so as to apply the suitable operating load to the operator. At the time of operations in the direct teaching mode, by turning a proportional gain to a small value, for example, a soft operating system can be realized. Namely, the motor 5 is torque controlled so as to apply suitable operating load to the operator corresponding to the value of this proportional gain.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an industrial robot having an arm which is oscillated by an actuator such as a servomotor and which performs a reproducing operation based on data obtained by a direct teaching operation. The present invention relates to a control device for an industrial robot that can easily perform a teaching operation in consideration of an operation load.

[0002]

2. Description of the Related Art Conventionally, industrial equipment equipped with this type of control device
As the robot, for example, JP-A-63-278777.
Known are those disclosed in the official gazette and Japanese Patent Laid-Open No. 1-234185.
Has been. In the industrial robot disclosed in each of the above publications,
At the tip of the robot arm, a handle for operation
With a force sensor that detects the external force applied to the steering wheel
The robot moves in the direction of the external force.
Based on the detection signal from the force sensor, the function built in the robot is
By controlling the torque or speed of the drive unit
Allows the operator to apply a slight force to the handle in the desired direction.
If you add it, the robot will follow its direction.
It is a thing. The control system in this case is based on the above force sensor.
Servo system using the detection signal of
It is realized by doing. That is, the tip of the robot arm
The force sensor attached to the
Can detect forces (x, y, z, α, β, γ)
Integrated (see Figure 3),
Force vector F applied to the tip of the arm _c(F_x, F
_y, F_z, Fα_,Fβ, Fγ) is detected. This power
Cuttle F_cIs a vector in the sensor coordinate system,
In order to drive each joint of the
Force vector F which is external force applied_cJoint drive equivalent to
Power is needed. That is, the torque vector τ (τ₁, Τ
₂,…, Τ_n) (Where n is the degree of freedom of the robot)
Then, the following formula is established.

[Equation 1] Therefore, if the above-mentioned servo system is a torque control type, the torque vector τ obtained by the above formula is output, and if the speed control type is the joint angular velocity vector obtained by the above formula, the target position is output as a feedback signal in the above servo system. By doing so, the robot is controlled to achieve the initial purpose.

[0003]

However, in the conventional industrial robot which is controlled as described above, since the Jacobian matrix in the above coordinate conversion formula is a function of the joint angle vector, complicated calculation is performed. It needs to be done in a timely manner and requires an expensive control device capable of high-speed processing. Also, when using the above formula,

[Equation 2] Since the joint angular velocity vector has an excessive value near the singular point where there is no and there is a risk of a dangerous situation for the operator, a special means is required to avoid this. Further, in the above-mentioned conventional industrial robot, there is an inconvenience in operation that the robot does not operate unless a handle with a force sensor attached is gripped and an operating force is applied. Therefore, the present invention was devised in view of the above circumstances, and an object thereof is to provide an industrial robot capable of easily performing a teaching operation in consideration of an operation load.

[0004]

In order to achieve the above object, the main means adopted by the present invention, which is the gist of the invention, comprises an arm swingably driven by an actuator and is obtained by direct teaching operation. In an industrial robot that performs a replay operation based on the data, a torque detection means that detects a torque acting around the swing axis of the arm, and a switching means that switches the operation mode between a direct teaching operation mode and a replay operation mode. And a control for torque-controlling the actuator so that an operating load is appropriately applied to the operator based on the torque signal from the torque detecting means when the operation mode is switched to the direct teaching operation mode by the switching means. An industrial robot according to a point including means.

[0005]

When the operation mode of the industrial robot is directly switched to the teaching operation mode and the operator (operator) supports a suitable portion of the robot to perform a teaching operation, the torque acting around the swing axis of the arm A torque signal is output from the torque detecting means in response to the above. Based on this torque signal, the actuator is torque-controlled so that an operating load is appropriately applied to the operator. The processing in the control device for the target value in this case is performed by executing a one-dimensional simple operation.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the accompanying drawings for the understanding of the present invention. The following embodiments are examples of embodying the present invention and are not of the nature to limit the technical scope of the present invention. FIG. 1 is a control block diagram of essential parts of an industrial robot according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a situation in which an operator performs a teaching operation on the industrial robot. In the vertical articulated industrial robot according to this embodiment, as shown in FIGS. 1 and 2, a motor 5 is connected to a swingable arm 3, for example, via a speed reducer 4. The motor 5 is an example of a servo actuator used as a swing drive source for the arm 3. Between the output shaft of the speed reducer 4 and the swing shaft of the arm 3, a torque detector 6 for detecting the torque acting around the swing shaft core of the arm 3 is provided. An angle detector 7 for detecting the swinging angle of the arm 3 is directly connected to 5. A pulse encoder or the like is applied as the angle detector 7, for example. The motor 5, the torque detector 6 and the angle detector 7 are connected to a control device 8, which controls the target position generator 9, the counter circuit 10, the differentiator 11, the integrator 12, and the multiplier 13. , A gravity compensator 14, a loop gain setting device 15, a filter 16, a power conversion device 17, and the like. In addition,
Although the above description is centered on the configuration of the arm 3, the other shaft elements are also configured in substantially the same manner as the case of the arm 3. Therefore, also in the following description, the description will be made with respect to this arm 3 and the description with respect to other shaft elements will be omitted.

Here, the gravity compensator 14 is an important element for ensuring the stability of the servo when the industrial robot is in a stationary state, and the arm 3 forming the s ₃ axis.
, And is required when controlling the motor 5 so that the torque acts in a direction in which the action of gravity in the vertical direction of the arm 2 constituting the s ₂ axis is canceled. In the embodiment, the gravity compensation term g (θ), which is positionally determined by the joint angle position θ of the arm 3, is reflected in the control system (see the formula described later). Therefore, the gravity compensator 14 is required in the vertical articulated industrial robot according to this embodiment, but is required in a so-called scalar type industrial robot in which the arm is swing-driven in the horizontal plane. Not be In the industrial robot having the above configuration, when the operation mode is switched from the reproduction operation mode to the teaching operation mode directly by the operator operating the switch box 1, for example, the angle signal and the torque from the angle detector 7 Based on the torque signal from the detector 6, the motor 5 is torque-controlled by the controller 8 so that an operation load is appropriately applied to the operator. The control procedure in this case will be described in detail below. In this case, the switch box 1 is directly switched to the teaching operation mode, and the operator carries out the teaching operation while supporting appropriate portions such as the arm 3 and the end effector. First, when the data θ of the current position of the arm 3 is input from the angle detector 7, the deviation θ that is the control target is based on this data θ.
_e is calculated. Then, θ _e is given by θ _e = θ−θ _ref . Here, θ _ref is the joint angle target position calculated by coordinate conversion after the trajectory calculation by the higher-level control device that controls the entire system, and its value is 0 during the direct teaching operation.

Then, based on the above θ _e , the multiplier 1
3. The integrator 12 and the differentiator 11 respectively calculate the torque component τ _P related to the proportional element, the torque component τ _I related to the integral element, and the torque component τ _D related to the differential element. Note that these _{values, τ P = K P · θ} e (K P ... proportional _{gain) ... τ I = K I ·} ∫θ e dt (K I ... integral _{gain) ... τ D = K D ·} dθ e / dt is given by (K _D ... differential gain) .... On the other hand, the torque signal from the torque detector 6 is fed back as a torque detection value τ after the noise is removed by the filter 16, and is output as a torque component τ _T related to the loop element from the loop gain setter 15. In this case, the tau _T is given by _{τ T = G T (τ P} -τ) (G T ... loop gain) .... Based on the torque component obtained as described above, the final torque target value tau _{re f} is calculated, based on the tau _ref, the motor 5 the power conversion apparatus 1
Torque is controlled via 7. In this case, τ _ref is represented by τ _ref = τ _P + τ _I + τ _D + τ _T + g (θ).

In the control system having the above configuration, in the direct teaching operation mode, a soft operation system can be realized by setting the proportional gain K _P to a small value, for example. That is, the torque of the motor 5 is controlled so that the operator appropriately receives an operation load according to the value of K _P.
On the other hand, in the reproduction operation mode, conversely, by setting the K _P to a large value that does not oscillate, automatic operation can be performed with the same accuracy as that of a general industrial robot that is generally used. Instead of the proportional gain K _P , the integral gain K _I or the differential gain K _D may be switched, or a combination of these may be switched appropriately to switch the control system. In addition, when performing work such as deburring or fitting during playback, which comes in contact with an object,
It is necessary to set the hardness (rigidity matrix) in the working coordinate system, that is, the xyz coordinate system. In this case

[Equation 3] From this, a so-called force control type industrial robot can be realized by sequentially setting K _IJ to the proportional gain K _P of the multiplier 13 in the control device 8.

[0010]

As described above, according to the present invention, in the industrial robot having the arm swingably driven by the actuator and reproducing based on the data obtained by the direct teaching operation, the swinging of the arm is performed. A torque detecting means for detecting a torque acting around the axis, a switching means for switching the operation mode between a direct teaching operation mode and a reproduction operation mode, and an operation mode for the direct teaching operation mode by the switching means. In this case, the industrial robot is characterized by comprising control means for controlling the torque of the actuator so that an operating load is appropriately applied to the operator based on the torque signal from the torque detecting means. In the direct teaching operation mode, the operator can easily perform the teaching operation while supporting an appropriate portion of the robot. The processing in the control device for the operation target value in this case is performed by executing a one-dimensional simple operation. Therefore, in the industrial robot, the teaching operation can be performed by the relatively simple and inexpensive control device based on the high-speed arithmetic processing. Further, in the control device configured as described above, since there is no singularity in principle as in the case of the conventional device described above, the safety for the operator is ensured and the singularity is avoided. There is no need to take any measures.

[Brief description of drawings]

FIG. 1 is a control block diagram of a main part of an industrial robot according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a situation in which an operator performs a teaching operation on the industrial robot.

FIG. 3 is a schematic block diagram of a control system of a conventional industrial robot.

[Explanation of symbols]

1 ... Switch box 2,3 ... Arm 4 ... Reducer 5 ... Motor 6 ... Torque detector 7 ... Angle detector 8 ... Control device 9 ... Target position generator 10 ... Counter circuit 11 ... Differentiator 12 ... Integrator 13 ... Multiplier 14 ... Gravity compensator 15 ... Loop gain setter 16 ... Filter 17 ... Power converter

Claims (1)

[Claims] 1. An industrial robot having an arm swingably driven by an actuator and performing a reproducing operation based on data obtained by a direct teaching operation detects a torque acting around the swing axis of the arm. Torque detecting means, switching means for switching the operation mode between the direct teaching operation mode and the reproduction operation mode, and the torque detecting means for switching the operation mode to the direct teaching operation mode by the switching means. An industrial robot comprising: a control unit that controls the torque of the actuator so that an operation load is appropriately applied to an operator based on a torque signal.