JPH0716898B2 - Manipulator joint control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a manipulator joint control device, and more particularly to joint control that eliminates the inconvenience of losing force sensation in a special posture in master-slave type bilateral force control. Regarding the device.

B. Summary of the Invention In the present invention, in bilateral force control with a master-slave type manipulator, the operating state near the singular point is judged and the slave side is placed in a controllable state with respect to the master side. This prevents malfunction, out-of-control or failure.

C. Conventional technology Operation-type manipulators such as master-slave manipulators employ so-called bilateral force control, in which the load on the slave side associated with the operation on the master side returns to the master side as a force sensation. This allows for dexterous operation. In this case, multiple joints are used, and the number of joints is typically 7 degrees of freedom including position 3 degrees of freedom, posture 3 degrees of freedom, and gripping 1 degree of freedom.
For example, in the joint configuration shown in FIG. 3, the joint 1 for swinging up and down the shoulder, the joint 2 for twisting the elbow, the bending joint 3 for the elbow, the bending joint 4 for the wrist, the joint 4 for the wrist, Bending joint 5 in the other direction (front and back directions in the drawing), joint 6 for twisting fingers,
It consists of a handle 7. With such a configuration, in the state shown in FIG. 3, force control (or force detection) can be performed on each joint in a typical posture, that is, a rotational moment acts on each joint (sensor), and The load in every direction (for example, external force ± F or torque T) can be detected by any joint.

D. Problems to be Solved by the Invention In the joint structure as described above, when the joints 1 to 7 are extended linearly as shown in FIG. 4, they act on the same axis as the arm extended linearly. The external force ± S to be applied cannot be detected or dealt with even by the joint because there is no sensor. Such a posture of extending the arm often occurs, for example, vertically downward or horizontally. In this posture where the joints are aligned, there is no sense of force, so
Excessive external force ± S causes the manipulator to be driven passively and cannot detect force, resulting in damage.
In the end, it became clear that it could cause serious malfunction or failure.

In order to solve the problem at this singular point, it is possible to attach a multi-directional force detector to the base part B to examine and control, but in that case, consider the state of the postures of all joints. It has to be calculated and is not practical.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and an object of the present invention is to provide a manipulator joint control device which detects a command for a special posture so that the joint does not become a special posture and the sense of force is not lost.

E. Means for Solving the Problems The present invention which achieves the above-mentioned object is, in a master-slave manipulator having articulated arms, a master and a slave each having an actuator and a sensor, and outputs of both the master and the slave. An amplifier that drives each actuator to reduce the deviation of the signal,
The rotation angle of at least two flexion joints of the master is detected, and the detection signal is compared with a signal for straightening each joint. As a result of this comparison, when a straightening command is output from the master, this command value is weighted And a control unit for activating the slave by turning on.

F. Example An example of the present invention will now be described with reference to FIGS. 1 and 2. In FIG. 2, the same parts as those in FIGS. 3 and 4 are designated by the same reference numerals. FIG. 1 shows a control block. In FIG. 1, M is a master or an operating device, S is a slave, and each has an actuator for operation and a rotation angle sensor. The output signals of the master M and the slave S are compared at the adding point E, and the signals are output through the amplifier A on the master M side and the amplifier B on the slave S side in the direction in which the deviation is reduced, and the actuator is output. It is driven.

Here, the signals of the rotation angle sensors are monitored for the two joints of the master M (for example, the joints 3 and 4 in FIG. 2),
The control unit C is provided for continuously comparing this signal with the constant condition K, and outputs the position deviation signal when the monitor signal reaches within the range of the condition K. The output of the control unit C is added by the addition unit D for amplification. The B side controls the slave S side.

The constant condition in this case is a signal instructing each of the joints 1 to 7 to form a straight line, and at least two joints 3, 4 are used to determine whether or not the joints are in a straight line that cannot cope with the external force. Is detected at. When the command value on the master M side is aligned, the slave S side controls by adding the deviation to the adder D to control the joints 3, 4
In other words, the angle .theta. And .alpha. Shown in FIG. 2 are obtained.

It is known to detect the working angle of each joint during the operation of the manipulator, but in addition to the conventional detection, the joints 3, 4
The angles θ and α of are detected and used. In this case, the joints 3 and 4 bend in the same plane, and adjacent joints are easy to use. This is because the control system is simple and the movement is easy to understand when they are in the same plane, and the reason why adjacent joints are used is the same.

During the operation, the angles θ and α of the joints 3 and 4 are constantly monitored, and this monitor is for determining whether or not the relationship of angle θ + α ≦ K (K is a constant) is satisfied. θ + α
When> K, there is no problem, but when θ + α ≦ K, a command is immediately issued to the joints 3 and 4 so that θ≈α≈K. As an example, when the arm is operating,
When + α becomes 15 ° or less, the slave side is operated by adding the weighted signal added to the position operation signals from the joints 3 and 4 and the master side so as to immediately set θ ≒ α ≒ 15 °. is there.

The value of 15 ° is because the value of K is set to a relatively small range in order to make the position fluctuation (lateral deviation) of the hand 7 slight when the command of θ≈α≈15 ° is changed. Therefore, a numerical value is appropriately selected to prevent lateral shift. Further, in order to prevent the lateral deviation of the fingertip 7, if the joint 1 is further actuated with a weighting signal of β≈K, the lateral deviation can be controlled as shown in FIG. As shown in FIG. 2, α and β are displaced in the same direction θ and in the opposite direction.

Thus, in a state where the arms are aligned, the joints are subjected to ± S external force or load acting from the hands 7 toward the shoulders.
Moment is generated in 1, 3, 4 and detects the presence of external force S,
It is possible to control and escape from overload.

As described above, it becomes possible to detect the singular point when the multi-joint arm issues a command to stretch the line almost linearly and when external force or load acts coaxially with the line, and The master side can react so that excessive force is not applied. It should be noted that it is possible to appropriately adopt a method of gradually increasing the addition increase of the weighted signal in an appropriate short time to prevent sudden operation.

Although the above embodiments have described adjacent joints that operate on the same plane, they may or may not be on the same plane as long as they control at least two joints.

G. Effect of the Invention As described above, according to the present invention, since the arm is not made to be a straight line and the joint is provided with a moment so that the hand position is substantially at the same position, the force sensation is not lost and the external force is not applied. And load can be recognized, and excessive load is not applied to prevent erroneous operation and breakdown.

[Brief description of drawings]

1 and 2 show an embodiment of the present invention. FIG. 1 is a control block diagram, FIG. 2 is a state diagram of an arm near a singular point, and FIG.
FIG. 4 is a simplified configuration diagram of an example of a 7-degree-of-freedom manipulator, and FIG. 4 is a state diagram of an arm connected in a straight line. In the drawing, 1 to 7 are joints, α, β and θ are angles, M is a master, S is a slave, A and B are amplifiers, C is a control unit, and D is an addition unit.

Claims (1)

[Claims] 1. A master-slave manipulator having articulated arms, a master and a slave each having an actuator and a sensor, and an amplifier for driving each actuator so as to reduce the deviation of the output signals of both the master and the slave. Then, the rotation angles of at least two flexion joints of the master are detected, and the detection signal is compared with a signal that straightens each joint. As a result of this comparison, when the straightening command is output from the master, this command value is set. A manipulator joint control device, comprising: a control unit that activates the slave by applying a weighted signal.