JP2013188859A - Actuator control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an actuator that does not take time to compute and can perform processing irrespective of a posture of a robot arm.SOLUTION: An actuator control device is connected between a robot body 1 and an end effector 2 and includes an actuator movable portion 3, an actuator fixed portion 4 and an actuator driving portion 5. Acceleration sensors 6 and 7 are installed in the actuator movable portion 3 and the actuator fixed portion 4 with the same installation angle. The actuator driving portion 5 is controlled based on relative acceleration of the actuator movable portion 3 to the actuator fixed portion 4 which is obtained by subtracting an output of the acceleration sensor 7 installed in the actuator fixed portion 4 from an output of the acceleration sensor 6 installed in the actuator movable portion 3, thereby moving the actuator movable portion 3 in relation to the actuator fixed portion 4.

Description

  The present invention relates to an actuator control device that detects acceleration in order to control a robot.

  In recent years, industrial robots are used in various fields from automobile manufacture to electronic component assembly, and there is a demand for performance capable of high-speed assembly work with higher accuracy. Accordingly, there is a need for a structure that does not damage the robot even if it touches the work target when the robot is operating at a relatively high speed.

  In addition, when performing assembly work such as precision mounting of semiconductor parts and MEMS (Micro Electro Mechanical Systems) parts, it is necessary to precisely position the actuator in accordance with the part that is the object, and contact caused by this contact. A structure that works while controlling so that the force does not become excessive is necessary.

  As one of the means for realizing the above function, a device capable of controlling mechanical impedance is connected between the robot body and the end effector for operating the work target to suppress the vibration of the movable part. And a method of controlling the contact force with the object.

  As a method for suppressing the vibration of the movable part, for example, Patent Document 1 discloses a pure acceleration component obtained by calculating a vertical component of acceleration from an angle with respect to a vertical direction of an acceleration sensor and subtracting a gravitational acceleration component from the calculated value. A method for suppressing vibration by feeding back to the drive unit is disclosed.

  Further, for example, in Patent Document 2, the relative acceleration signal of the movable body with respect to the fixed body is detected, and the inertial reaction force is applied to the movable body based on the relative acceleration signal, thereby suppressing the fine vibration of the movable body. A method is disclosed.

JP 2005-228322 A JP-A-6-71532

However, for example, a conventional vibration control method such as Patent Document 1 needs to use a trigonometric function when obtaining a pure acceleration, and takes a long time for calculation processing, and thus has a problem that it is not suitable for high-speed control.
In addition, when an angle detector is separately provided to detect the posture of the robot arm, there is a problem that the apparatus becomes complicated. On the other hand, when the posture of the robot arm is obtained by calculation without the angle detector. However, since the calculated posture has an error, there is a problem that it does not necessarily match the actual posture.

  Further, for example, the conventional method for suppressing micro-vibration as disclosed in Patent Document 2 is based on the premise that the fixed portion and the movable portion are used in a horizontal state. There is a problem that no consideration is given to the state of being inclined and the state in which the fixed portion is moved by an external force.

  The present invention has been made in order to solve the above-described problems, and provides a control device for an actuator that does not take time for calculation processing and can perform processing regardless of the posture of the robot arm. The purpose is to provide.

  In order to achieve the above object, the present invention provides an actuator control device that is connected between a robot body and an end effector that operates a work target, and includes a movable part, a fixed part, and a drive part. Each of the fixed parts has an acceleration sensor installed at the same mounting angle, and is obtained by subtracting the output of the acceleration sensor installed in the fixed part from the output of the acceleration sensor installed in the movable part. The movable part is moved relative to the fixed part by controlling the drive part based on the relative acceleration of the movable part to the fixed part.

According to the actuator control device of the present invention, the calculation of the actuator movable portion relative to the actuator fixed portion is performed by a calculation process that only subtracts the output of the same acceleration sensor installed at the same mounting angle on the movable portion and fixed portion of the actuator. Since it is possible to detect relative acceleration and it is not necessary to perform complicated calculation using trigonometric functions, it is possible to control the processing lightly and at high speed.
Further, since it is possible to perform processing regardless of the posture of the robot arm, it is not necessary to detect the posture of the robot arm and to calculate it.

It is a figure which shows the outline of the actuator which concerns on Embodiment 1 of this invention, and a robot provided with the same. In the actuator control apparatus according to Embodiment 1 of the present invention, it is an explanatory diagram about measurement of acceleration when the moving direction of the movable part is the vertical direction. It is a flowchart which shows the flow of a process of the control apparatus of the actuator which concerns on Embodiment 1 of this invention. It is explanatory drawing about calculation of the relative acceleration of the control apparatus of the actuator in the case shown in FIG. In the actuator which concerns on Embodiment 1 of this invention, it is explanatory drawing about the measurement of an acceleration in case the moving direction of a movable part is angle (theta) 1 with respect to a horizontal surface. It is explanatory drawing about calculation of the relative acceleration of the control apparatus of the actuator in the case shown in FIG.

Embodiment 1 FIG.
FIG. 1 is a diagram schematically showing an actuator and a robot including the actuator according to Embodiment 1 of the present invention. As shown in FIG. 1, this actuator is connected between a robot body 1 and an end effector 2 for operating a work target, and includes an actuator movable part 3, an actuator fixing part 4 and an actuator driving part 5 (not shown). I have. The actuator moving unit 3 is moved with respect to the actuator fixing unit 4 by controlling the actuator driving unit 5.
An acceleration sensor 6 is installed in the actuator movable section 3 and an acceleration sensor 7 is installed in the actuator fixing section 4 (see FIG. 2). These acceleration sensors measure acceleration and feed back to the actuator drive section 5. . That is, the actuator driving unit 5 is controlled based on the outputs of the acceleration sensors 6 and 7.

  FIG. 2 is an explanatory diagram for the measurement of acceleration by the actuator control apparatus according to Embodiment 1 of the present invention, where the moving direction of the actuator movable portion 3 is the vertical direction (the angle with respect to the horizontal plane is 90 °). Show. As shown in FIG. 2, this actuator is a one-axis type actuator in which the actuator movable portion 3 can move only in one direction with respect to the actuator fixing portion 4. The acceleration sensor 6 and the acceleration sensor 7 are installed so that the mounting angles are equal to the moving direction of the actuator movable portion 3. Further, the upward arrow in FIG. 2 indicates that the actuator movable portion 3 is moved upward at the acceleration α1, and the actuator fixing portion 4 is moved upward at the acceleration α2. The downward arrow is a gravity force. It shows that the acceleration G is working.

  Next, the operation will be described. FIG. 3 is a flowchart showing processing of the actuator control apparatus according to Embodiment 1 of the present invention. Here, as shown in FIG. 2, a case will be described in which the actuator movable portion 3 moves in the vertical direction at an acceleration α1 and the actuator fixing portion 4 moves in the vertical direction at an acceleration α2.

  First, the acceleration of the actuator movable part 3 is detected (step ST1). The output of the acceleration sensor 6 installed in the actuator movable portion 3 indicates “α1-G”, and includes not only the moving acceleration component α1 of the actuator movable portion 3 but also the gravitational acceleration component G. Next, the acceleration of the actuator fixing unit 4 is detected (step ST2). The output of the acceleration sensor 7 installed in the actuator fixing unit 4 indicates “α2−G” and includes not only the moving acceleration component α2 of the actuator fixing unit 4 but also the gravitational acceleration component G.

  Here, since the acceleration sensor 6 and the acceleration sensor 7 are installed so that their mounting angles are equal to the moving direction of the actuator movable portion 3, the gravitational force included in the output of the acceleration sensor 6 and the output of the acceleration sensor 7 is included. The magnitude of the acceleration component G is equal.

Therefore, by subtracting the output of the acceleration sensor 7 from the output of the acceleration sensor 6, the relative acceleration of the actuator movable portion 3 with respect to the actuator fixing portion 4 is calculated (step ST3). As shown in FIG. ”And does not include the gravitational acceleration component G. FIG. 4 is an explanatory diagram for calculating the relative acceleration of the actuator control device in the case shown in FIG.
By feeding back the relative acceleration not including the gravitational acceleration component G to the actuator drive unit 5 (step ST4), vibration of the actuator movable unit 3 can be suppressed and mechanical impedance can be controlled. As a result, the vibration of the end effector 2 can be suppressed and the contact force with the object can be controlled.

  Next, the case where the angle with respect to the horizontal plane of the moving direction of the actuator movable part 3 is set arbitrarily will be described. FIG. 5 is an explanatory diagram for measuring acceleration by the actuator according to the first embodiment of the present invention, and shows a case where the angle of the moving direction of the actuator movable portion 3 with respect to the horizontal plane is set to θ1. As shown in FIG. 5, the actuator movable unit 3 is a single-axis type actuator that can move in only one direction with respect to the actuator fixing unit 4. The acceleration sensor 6 and the acceleration sensor 7 are installed so that the mounting angles are equal to the moving direction of the actuator movable portion 3. Further, the arrow in the θ1 direction with respect to the horizontal plane in FIG. 5 indicates that the actuator movable portion 3 moves in this direction at an acceleration α1, and the actuator fixing portion 4 moves in this direction at an acceleration α2. The downward arrow indicates that the gravitational acceleration G is working.

  The operation in this case is similar to the flowchart shown in FIG. Here, as shown in FIG. 5, the actuator movable portion 3 is moved in the θ1 direction with respect to the horizontal plane at an acceleration α1, and the actuator fixing portion 4 is moved in the θ1 direction with respect to the horizontal plane at the acceleration α2. Think about when you are.

  First, the acceleration of the actuator movable part 3 is detected (step ST1). The output of the acceleration sensor 6 installed in the actuator movable portion 3 indicates “α1-Gcos (90 ° −θ1)”, and not only the moving acceleration component α1 of the actuator movable portion 3 but also the angle θ1 in the moving direction of the actuator movable portion 3. The gravitational acceleration component G is taken into consideration. Next, the acceleration of the actuator fixing unit 4 is detected (step ST2). The output of the acceleration sensor 7 installed in the actuator fixing portion 4 indicates “α2−Gcos (90 ° −θ1)”, and not only the moving acceleration component α2 of the actuator fixing portion 4 but also the angle θ1 in the moving direction of the actuator fixing portion 4. The gravitational acceleration component G is taken into consideration.

  Here, since the acceleration sensor 6 and the acceleration sensor 7 are installed so that their mounting angles are equal to the moving direction of the actuator movable portion 3, the gravitational force included in the output of the acceleration sensor 6 and the output of the acceleration sensor 7 is included. The magnitude of the acceleration component G and the angle θ1 in the moving direction of the actuator movable portion 3 are equal.

  However, even if the output of the acceleration sensor 6 including the gravitational acceleration component Gcos (90 ° −θ1) considering the angle θ1 in the moving direction is fed back to the actuator driving unit 7, the gravitational acceleration component “Gcos (90 ° −θ1)” Therefore, the vibration and mechanical impedance of the actuator movable part 3 cannot be controlled well.

Therefore, by subtracting the output of the acceleration sensor 7 from the output of the acceleration sensor 6, the relative acceleration of the actuator movable portion 3 with respect to the actuator fixing portion 4 is calculated (step ST3). As shown in FIG. The value does not include the gravitational acceleration component G and the angle θ1 in the moving direction of the actuator movable portion 3. FIG. 6 is an explanatory diagram for calculating the relative acceleration of the actuator control apparatus in the case shown in FIG.
By feeding back the gravitational acceleration component G and the relative acceleration that does not include the angle θ1 of the moving direction of the actuator 3 to the actuator driving unit 5 (step ST4), vibration of the actuator moving unit 3 can be suppressed or mechanical. Impedance can be controlled. As a result, the vibration of the end effector 2 can be suppressed and the contact force with the object can be controlled.

  That is, the process can be performed regardless of the influence of the gravitational acceleration and the posture of the robot arm, and it is not necessary to detect and calculate the gravitational acceleration and the posture of the robot arm.

  As described above, even when the actuator fixing portion 4 and the actuator movable portion 3 are inclined with respect to the horizontal direction or when the actuator fixing portion 4 is moved by an external force, the actuator movable portion 3 with respect to the actuator fixing portion 4 By simply calculating the relative acceleration, it is possible to suppress the vibration of the actuator movable portion 3 and to control the mechanical impedance, and to control the vibration of the end effector 2 and the contact force with the object. be able to.

  Even if there is an offset in the acceleration sensor, if the acceleration sensors installed in the actuator movable portion 3 and the actuator fixing portion 4 are the same, the individual difference can be almost ignored and the offset value is almost the same. Since they are equal, the relative acceleration obtained by this subtraction can be a value that does not include the offset.

As described above, according to the first embodiment of the present invention, the actuator movable portion 3 and the actuator fixing portion 4 are provided with the acceleration sensors 6 and 7 at the same mounting angle, respectively. Actuator drive unit based on the relative acceleration of the actuator movable unit 3 with respect to the actuator fixed unit 4 obtained by subtracting the output of the acceleration sensor 7 installed in the actuator fixed unit 4 from the output of the acceleration sensor 6 installed in the actuator Since the actuator movable portion 3 is moved relative to the actuator fixed portion 4 by controlling 5, the relative acceleration of the actuator movable portion 3 with respect to the actuator fixed portion 4 can be detected by a calculation process only by subtraction. Possible and requires complex calculations using trigonometric functions Since living in no, it is possible to control the process lightly and quickly.
Further, since it is possible to perform processing regardless of the posture of the robot main body 1, it is not necessary to detect the posture of the robot main body 1 and to calculate it.
Furthermore, even if there is an offset in the acceleration sensors 6 and 7, the offset is canceled in the subtraction process, so that an error due to the offset does not occur in the relative acceleration.

  In the first embodiment of the present invention, the single axis type actuator in which the actuator movable portion can move only in one direction with respect to the actuator fixed portion has been described. However, the actuator movable portion has X, Y, It goes without saying that the same effect can be obtained when an acceleration sensor capable of detecting the acceleration in the three axes of X, Y, and Z is installed at the same mounting angle on the actuator movable in the three axes of Z.

  Further, in the present invention, any constituent element of the embodiment can be modified or any constituent element of the embodiment can be omitted within the scope of the invention.

DESCRIPTION OF SYMBOLS 1 Robot body 2 End effector 3 Actuator movable part 4 Actuator fixed part 5 Actuator drive part 6 Acceleration sensor 7 Acceleration sensor

Claims (1)

In an actuator control device that is connected between a robot body and an end effector that operates a work target, and includes a movable part, a fixed part, and a drive part.
In the movable part and the fixed part, acceleration sensors are respectively installed at the same mounting angle,
Controlling the drive unit based on a relative acceleration of the movable unit with respect to the fixed unit, which is obtained by subtracting an output of the acceleration sensor installed in the fixed unit from an output of the acceleration sensor installed in the movable unit. The movable part is moved with respect to the fixed part by the actuator control apparatus.

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