JP3612637B2 - Manipulator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a manipulator that performs a six-degree-of-freedom motion, and more particularly to a manipulator that can be applied to automatic assembly, positioning devices, and the like.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a manipulator configured to move a movable member relative to a base member, a parallel link manipulator in which the base member and the movable member are connected by six sets of extendable link pairs is known. This mechanism is characterized by a configuration in which the position and posture of the movable member are controlled by expanding and contracting the linear motion portion of each link pair, and the advantages include the following.
[0003]
First, by adopting a structure in which each link pair is accommodated between the base member and the movable member, a motion mechanism having 6 degrees of freedom (position 3 degrees of freedom, posture 3 degrees of freedom) can be configured compactly.
In addition, since the force applied to the movable member is distributed to a relatively large number of structural parts such as six link pairs, the result is high rigidity.
Furthermore, since the play of the joint mechanism of the link pair is averaged, the accuracy becomes higher than that of a normal 6-DOF industrial robot.
[0004]
[Problems to be solved by the invention]
However, the six link pair configuration as described above has a problem in that mutual interference occurs between these parallel links, resulting in a narrow operating range.
The present invention has been made to solve the above-described problems in the prior art, and an object of the present invention is to provide a manipulator that has no mutual interference between each link pair and has a wide movable region.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, a manipulator according to the present invention is a manipulator including a base member, a movable member, and three sets of link pairs connecting them, and each link pair is transferred from the base member to the movable member. Oppositely connected by four joints of a rotary type first joint, a rotary type second joint, a direct acting type third joint, a ball socket type fourth joint, and a first link and a direct acting link connecting them, and The rotary first joint and the rotary second joint base include a rotary actuator having an encoder for detecting a rotation angle,
The axial center of the rotary second joint and the axial center of the rotary first joint are on the same plane and orthogonal to each other,
The shaft center of the rotary second joint and the shaft center of the linear link are crossed, and the rotary second joint and the linear motion third joint are directly connected without a link. And
[0006]
In the manipulator according to the present invention as described above, since the movable member and the base member are connected by a small number of link pairs, there is almost no mutual interference area between the link pairs, and thus the movable area becomes wide.
[0007]
The manipulator according to the present invention is characterized in that the ball socket type fourth joint is replaced with three rotary joints and a link connecting them. With this configuration, a wider movable range can be realized, and the play of the mechanism can be kept low.
[0008]
The manipulator according to the present invention is configured by intersecting the axis center of the rotary second joint and the axis center of the linear link and directly connecting the rotary second joint and the linear joint without a link. It is characterized by that. With this configuration, the number of component parts is reduced, and the calculation for obtaining the position and orientation of the movable part from the angle is simplified.
[0009]
The manipulator according to the present invention is characterized in that the position and orientation of the movable member are obtained based on the angle detected by the encoder. With this configuration, it is not necessary to provide an extra sensor for observing the position and orientation of the movable member, and the position and orientation of the movable member are required at low cost.
[0010]
The manipulator according to the present invention is characterized in that a linear encoder that detects the length of the linear motion link 8 is provided in the linear motion joint. With this configuration, the calculation for obtaining the position and orientation of the movable member can be simplified, and thus high-speed calculation is possible.
[0011]
The manipulator according to the present invention is characterized in that a force applied between the base member and the movable member is detected and fed back to the actuator. With this configuration, it can be applied to work that requires observation or control of a state where a force is applied.
[0012]
The manipulator according to the present invention is configured such that a torque sensor is attached to each of the rotary actuators, and a force applied between the base member and the movable member is detected based on an output from the torque sensor. . This configuration enables a device for measuring force in a compact manner.
[0013]
The manipulator according to the present invention includes a six-axis force sensor attached to the movable member, and detects a force applied between the base member and the movable member based on an output from the six-axis force sensor. Features. With this configuration, the force in the Cartesian space is directly measured.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 1 is an explanatory diagram showing a schematic configuration of a main part of a manipulator according to an embodiment of the present invention. FIG. 2 is a top view of the main part of the manipulator shown in FIG.
As shown in FIG. 1, the manipulator M according to this embodiment includes a base member 1, a movable member 9, and three sets of link pairs L1 to L3 that connect them.
[0015]
The link pair L1 is directed from the base member 1 to the movable member 9, and includes a rotary first joint 2 with a rotary motor 2A, a rotary second joint 3 with a rotary motor 3A, a direct acting third joint 4, a ball The socket-type fourth joint 5 is connected by four joints.
Furthermore, the rotary type first joint 2 and the rotary type second joint 3 are coupled by a first link 6, and the rotary type second joint 3 and the linear motion type third joint 4 are coupled by a second link 7. The three joints 4 and the ball socket type fourth joint 5 are coupled by a linear motion link 8.
[0016]
Similarly, the link pair L2 includes a rotary first joint 12 with a rotary motor 12A, a rotary second joint 13 with a rotary motor 13A, a direct acting third joint 14, and a ball socket type fourth joint 15. Are connected by four joints.
Further, the rotary first joint 12 and the rotary second joint 13 are coupled by a first link 16, and the rotary second joint 13 and the direct acting third joint 14 are coupled by a second link 17. The three joints 14 and the ball socket type fourth joint 15 are connected by a linear motion link 18.
[0017]
Further, the link pair L3 similarly includes a rotary first joint 22 with a rotary motor 22A, a rotary second joint 23 with a rotary motor 23A, a direct acting third joint 24, and a ball socket type fourth joint 25. Are connected by four joints.
Further, the rotary first joint 22 and the rotary two joint 23 are connected by a first link 26, and the rotary second joint 23 and the direct acting third joint 24 are connected by a second link 27, and a direct acting third joint. 24 and the ball socket type fourth joint 25 are connected by a linear motion link 28.
[0018]
Moreover, the connection part of the base member 1, the movable member 9, and each link pair L1-L3 has comprised the equilateral triangle as shown in FIG.
[0019]
FIG. 3 is a perspective view showing in detail the configuration of the link pair L1. FIG. 4 is a side view of the link pair L1.
As shown in the figure, the first and second rotary type first and second joints 2 and 3 counted from the base member 1 are equipped with rotary motors 2A and 3A, respectively. Encoders 2C and 3C for measuring the rotation angle are provided, and torque sensors 2B and 3B for measuring torque are provided.
[0020]
By constructing a control system corresponding to the above configuration as shown in FIG. 5, it is possible to control each joint angle and control the position and posture of the movable member with respect to the base member with six degrees of freedom. Become.
In the control system shown in the figure, data 101a given from the target position block 101 is converted by the inverse kinematics conversion block 102, and the angle output 102a from the inverse kinematics conversion block 102 is based on encoder (for example, 2C) information. This is the reference input for the speed / position feedback loop.
[0021]
Moreover, the structure which makes the length of the 2nd link 7 in FIG. 1 0 is also possible. This is embodied as a configuration in which the axis center of the rotary second joint 3 intersects the axis center of the linear motion link 8.
With this configuration, it is possible to simplify the inverse kinematic transformation (converting the position coordinates in the Cartesian space to the joint angle coordinates) performed in the block 102 in the control system of FIG. As a result, a high-speed servo control loop can be configured, or it can be adapted to control by a microcomputer with low performance.
[0022]
Further, by calculating based on an output value 2Ba of a torque sensor (for example, 2B or 3B in FIG. 3) provided in each motor, a 6-dimensional vector F (force component) in a Cartesian space between the movable member and the base member is calculated. Fx, Fy, Fz, and torque components Tx, Ty, Tz). This calculation can be performed in the torque-force coordinate conversion block 103 in FIG.
[0023]
FIG. 6 is an explanatory diagram showing a schematic configuration of a main part of a manipulator according to the second embodiment of the present invention.
As shown in FIG. 6, the manipulator M2 of the second actual form according to the present invention replaces the ball socket type fourth joint 5 in the first embodiment with three rotary joints 31, 32, 33. Constitute.
[0024]
Ordinary ball socket type spherical bearings have the advantage of being able to form a joint with 3 degrees of freedom in a compact manner. However, if the clearance between the bearing and the shaft is large, the accuracy may be degraded, and the allowable operating range is limited. Narrowing may limit the entire movable range. In view of this, in the present embodiment, the ball socket type spherical bearing is replaced with an ordinary rotary type bearing to constitute a joint, whereby a mechanism with high accuracy and a large operating range can be obtained.
[0025]
The third actual form according to the present invention is configured by providing a linear encoder in the direct acting third joint 4 of FIG.
With this configuration, the movement distance (movement length) of the linear motion link 8 can be measured, so that the calculation in the inverse kinematics conversion block 102 and the torque-force coordinate conversion block 103 in FIG. 5 can be further simplified and the accuracy can be improved. Can be improved.
[0026]
FIG. 7 is an explanatory diagram illustrating a schematic configuration of a main part of a manipulator according to the fourth embodiment.
In the fourth embodiment, instead of providing a torque sensor for each motor in the first embodiment, a six-axis force sensor 60 is provided on the movable member, and three link pairs L11 to L13 are provided. Composed. The force applied to the movable member 9 can be directly measured by the six-axis force sensor 60, and the force F in the Cartesian space can be controlled with high accuracy.
[0027]
An example of the control system of the manipulator according to the fourth embodiment is shown in FIG.
In the figure, based on the information F obtained from the force sensor 60, the coordinate conversion block 110 performs primary conversion based on the position and orientation of the movable member 9. The compliance output of the movable member 9 can be controlled by multiplying the conversion output 110a by a compliance gain by the multiplier 111 and adding it to the output 112a from the target position.
[0028]
Further, the difference between the converted output 110a and the output 113a from the target force is integrated by the integrator 114, and the result obtained by multiplying the multiplier 115 by the force control gain is added to the output 112a from the target position, thereby obtaining the target force. The following force control becomes possible.
[0029]
【The invention's effect】
As described above in detail, the manipulator according to claim 1 of the present invention includes a base member, a movable member, and three sets of link pairs connecting them, and each link pair is directed from the base member to the movable member in order. The rotary type first joint, the rotary type second joint, the direct acting type third joint, the four joints of the ball socket type fourth joint, and the first type link and the direct acting link that connect them, and the rotary type first joint. Since the one joint and the rotary type second joint base are provided with an actuator having an encoder for detecting the rotation angle, this configuration requires only three link pairs, reducing mutual interference between the links and reducing the movable range. A wide 6-DOF manipulator can be realized. Further, the number of components can be reduced as compared with the conventional parallel link manipulator, and a manipulator that is inexpensive and excellent in reliability can be realized.
In addition, the axis center of the rotary second joint and the axis center of the rotary first joint are arranged on the same plane and orthogonal to each other, and the axis center of the rotary second joint and the axis center of the linear link are Since it intersects and directly connects the rotary second joint and the direct acting third joint without a link, the number of components can be reduced. In addition, since the calculation for obtaining the position and orientation of the movable part from the angle can be simplified, high-speed calculation is possible. Also, control using an inexpensive microcomputer with a relatively slow processing speed is possible.
[0030]
Since the manipulator according to claim 2 of the present invention is configured by replacing the ball socket type fourth joint with three rotary type joints and a link connecting them, a wider movable range can be obtained. In addition, the backlash of the mechanism can be kept low.
[0032]
Since the manipulator according to claim 3 of the present invention obtains the position and posture of the movable member based on the angle detected by the encoder, an extra sensor for observing the position and posture of the movable member is provided. The position and posture of the movable member can be obtained without any problem.
[0033]
Since the manipulator according to claim 4 of the present invention is configured to include a linear encoder that detects the length of the linear motion link in the linear motion joint, the calculation for obtaining the position and orientation of the movable member is performed. It can be simplified, and thus high-speed computation is possible. Alternatively, control by a relatively low performance microcomputer is also possible.
[0034]
Since the manipulator according to claim 5 of the present invention is configured to detect a force applied between the base member and the movable member and feed back to the actuator, it is necessary to observe or control a state where the force is applied. It is possible to apply to the work with.
[0035]
Since the manipulator according to claim 6 of the present invention attaches a torque sensor to each rotary actuator and detects the force applied between the base member and the movable member based on the output from the torque sensor, The apparatus which measures force to the used compact can be comprised.
[0036]
A manipulator according to a seventh aspect of the present invention includes a six-axis force sensor attached to the movable member, and detects a force applied between the base member and the movable member based on an output from the six-axis force sensor. Therefore, the force in the Cartesian space can be measured directly, and thus a highly accurate force control system can be configured.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a schematic configuration of a main part of a manipulator according to an embodiment of the present invention.
FIG. 2 is a top view of a main part of the manipulator shown in FIG.
3 is a perspective view showing a configuration of a link pair shown in FIG. 1. FIG.
4 is a side view of the link pair shown in FIG. 3;
FIG. 5 is a chart of a control system of the manipulator shown in FIG.
FIG. 6 is an explanatory diagram showing a schematic configuration of a main part of a manipulator according to another embodiment of the present invention.
FIG. 7 is an explanatory diagram showing a schematic configuration of a main part of a manipulator according to another embodiment of the present invention.
8 is a chart of a control system of the manipulator shown in FIG.
[Explanation of symbols]
M Manipulator L1 Link pair L2 Link pair L3 Link pair 1 Base member 2, 12, 22 Rotary type first joint 2A, 12A, 22A Motor 2B, 3B Torque sensor 2C, 3C Encoder 3, 13, 23 Rotary type second joint 3A , 13A, 23A Motor 4, 14, 24 Direct acting third joint 5, 15, 25 Ball socket type fourth joint 6, 16, 26 First link 7, 17, 27 Second link 8, 18, 28 Direct acting Link 9 Movable member 60 Axial force sensor

Claims (7)

A manipulator comprising a base member, a movable member, and three sets of link pairs connecting them, wherein each link pair is directed from the base member to the movable member, and in turn a rotary first joint and a rotary second joint 4 joints of a linear motion type third joint and a ball socket type 4th joint, and a first link and a linear motion link connecting them, and the rotary type first joint and the rotary type second joint base Has a rotary actuator with an encoder that detects the rotation angle,
The axial center of the rotary second joint and the axial center of the rotary first joint are on the same plane and orthogonal to each other,
The axial center of the rotary second joint and the axial center of the linear link are crossed, and the rotary second joint and the linear third joint are directly connected without a link. And manipulator. 2. The manipulator according to claim 1, wherein the ball socket type fourth joint is constituted by replacing three rotation type joints and a link connecting them. The manipulator according to claim 1 or 2, wherein the position and posture of the movable member are obtained based on an angle detected by the encoder. The manipulator according to claim 1, wherein a linear encoder that detects a length of the linear motion link is provided in the linear motion joint. The manipulator according to claim 1, wherein a force applied between the base member and the movable member is detected and fed back to the actuator. 2. The manipulator according to claim 1, wherein a torque sensor is attached to each rotary actuator, and a force applied between the base member and the movable member is detected based on an output from the torque sensor. The six-axis force sensor is attached to the movable member, and the force applied between the base member and the movable member is detected based on the output from the six-axis force sensor. Manipulator.

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