JPH0712596B2 - Robot arm wire-interference drive system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire interference driving system for driving a robot arm.

[0002]

2. Description of the Related Art A robot arm has a plurality of links and a plurality of joints connecting the links. The robot arm has multiple links from the link at the base end closest to the drive system side to the link at the tip end for working, and adjacent ones of these links are connected by joints, and each link is generated. The force to do is determined by the torque of each joint. Each joint is driven by an actuator.

However, since the actuator for driving the joint has a large weight, it is disadvantageous in terms of the output weight ratio if the actuator is directly attached to the joint, and it is particularly advantageous to attach the actuator to the joint near the hand of the robot arm. Instead, it is necessary to mount the actuator at a position closer to the drive system side than the target joint portion and transmit the driving force from the actuator to the target joint portion by some means.

Such a wire / pulley drive system is, for example, a Stanford / JPL hand (Robot).
Hands and the Mechanicals o
fManipulation by M.F. T. Ma
son and K.S. J. Salisbury-
The MIT Press and CT arm (Hirose,
Ma, "Development of Wire-Interference Driven Articulated Manipulator", Proceedings of the Society of Instrument and Control Engineers, Vol. 26, N
o11,).

[0005]

However, in these conventional techniques, for example, in the Stanford / JPL hand method, the tension of each wire is measured at one place, and the influence of friction loss of the pulley cannot be ignored. The CT arm method is 2 for n-joint robot arm.
N wires are required, the number of wires required is large, and the structure of the drive system is complicated. For this reason, it is desired to develop a wire interference drive system for a robot arm that is lighter in weight, requires fewer wires, is slimmer, has better controllability, and can be manufactured at low cost.

The present invention has been made in view of the above circumstances and is lightweight and requires a small number of wires.
It is slimmer, cheaper to manufacture, more wire can be applied to the joint closer to the base, and even if a uniform wire drive system is used, a greater torque can be generated to the joint closer to the base. , Wire-drive system component parts can be standardized, and each joint torque can be directly measured by the tension actuated torque sensor arranged near each joint axis. An object of the present invention is to provide a wire interference drive system for a robot arm that can eliminate the influence of friction loss of the pulley section by feeding back the joint torque to the control system.

[0007]

To solve this problem, the wire interference drive system of the robot arm of the present invention is n
This is a wire interference drive system for driving a robot arm having a number of joints, in which each joint is installed with the same number of pulleys as the number of wires hung on it so that they can rotate independently of each other, and the smallest even number exceeding n. Wire for each joint shaft is wound around the pulley for one or more turns, passes through the joint shaft, and is hung on the joint shaft.
When the number of wires is the same as the number of wires that hang on the joint axis next to the most proximal end side, two of the wires that hang on the joint axis are on the link member on the most distal side of the joint axis. Fix it, two wires hang on the joint at the tip,
The smallest even number of wires exceeding n for the proximalmost joint
And the (n−i) th joint from the most proximal end is (i
+1) minimum even number of wires are applied, and the even number of wires applied to each joint axis is the total number of the same number of forward rotation wires and reverse rotation wires, and the tension of each wire is It is characterized by controlling and realizing a predetermined torque of a target joint.

[0008]

Operation: n link members are connected by n joints, and the nth joint from the base end has two joints, the (n-1) th joint has four joints, and the (n-2) th joint. There are 4 joints, ... (n-
The i) th joint has a minimum even number of wires exceeding (i + 1), ..., The first joint has a minimum even number of wires exceeding n, and the tension of each wire is controlled. Generate a predetermined torque at the target joint. To do so, first determine the set of target torques for each joint, find the set of wire-tension that satisfies the set of target torques, and the axial force of the joint at the most proximal end is zero, and then determine the minimum set in that set. Using n times the wire tension as the set value of the axial force of the joint at the most proximal end, obtain a set of target torque and a set of wire tension that satisfies the set value of the axial force of the most proximal joint. . In addition, torque servo is performed using the feedback signal from each joint tension differential type sensor to eliminate the effect of friction loss in the pulley section.

[0009]

The details of the present invention will be described below with reference to the drawings showing the embodiments. FIG. 1 shows a robot arm 1 having seven joints. The robot arm 1 is provided with a link member L ₁ over L ₇ to the tip portion of the hand-side from the proximal end of the drive system side, each link member L ₁ -L ₇ are adjacent link member and joint J ₁ -J ₇ Are connected with. On the joint axes Z ₁ -Z ₇ of the joints J ₁ -J _7, the same number of pulleys P (P ₁₁ -P ₇₂ ) as the number of wires W passing therethrough are independently rotatably installed.

The connection state of each component is as follows. I-th
The pulley P is rotatably connected to the shaft except in the following cases. The link L _i and the link L _i-1 are rotatably connected via the Z _i axis. The idle pulley a _i rotates the movement direction of the cable by 90 degrees. That is, the joint axis Z ₁ of the joint J _1, rotation is established capable independently pulley P ₁₁ -P _18.

A pulley P ₂₁ -is attached to the joint axis Z ₂ of the joint J _2.
P ₂₈ is installed so that it can rotate independently. Pulleys P ₃₁ -P ₃₆ are independently rotatably installed on the joint axis Z ₃ of the joint J ₃ . Pulleys P ₄₁ -P ₄₆ are independently rotatably installed on the joint axis Z ₄ of the joint J ₄ . The joint axis Z ₅ of the joint J _5, rotation is established capable independently pulley P ₅₁ -P _54. Pulleys P ₆₁ -P ₆₄ are independently rotatably installed on the joint axis Z ₆ of the joint J ₆ . Pulleys P ₇₁ -P ₇₂ are independently rotatably installed on the joint axis Z ₇ of the joint J ₇ .

The smallest even number of wires W _{1 to} n + 1 or n + 2 exceeding the number of joints n (8 in the case of this embodiment)
Book) and wrap it around the pulleys P ₁ -P ₇₂ as described below. The even number of wires hung on each joint axis is the total number of the same number of wires for forward rotation and wires for reverse rotation. Idle pulley a ₁₁ −
a ₇₁ is used to change the direction of the wire by 90 degrees.

Each wire-driving path is as follows. From (wire -1) wire -1 driveline, wound around the pulley P _11, passes through the idle pulley a _11, a pulley P ₂₁
Around the idle pulley a ₁₂ and then around the pulley P ₃₁ by 1.25 turns around the idle pulleys a ₁₃ and a _14.
Passing around the pulley P ₄₁ , passing around the idle pulley a ₁₅ , passing around the pulley P ₅₁ for 1.25 turns, passing through the idle pulley a ₁₆ , passing around the pulley P ₆₁ ,
It is wound around the pulley P ₇₁ once and is fixed to the link member L ₇ .

(Wire-2) From the wire-2 drive system, it is wound around the pulley P ₁₂ once, passes through the idle pulleys a ₂₁ and a _22, and is wound around the pulley P ₂₂ once.
₂₃ , a ₂₄ , one turn around pulley P ₃₂ , idle pulley a ₂₅ , one turn around pulley P ₄₂ , idle pulleys a ₂₆ and a ₂₇ , and 1.5 on pulley P ₅₂ .
With peripheral winding, passes through the idle pulley a _28, a pulley P ₆₂
Once-wound with the, once-wound with a pulley P71, is secured to the link member L _7.

(Wire-3) From the wire-3 drive system, it is wound around the pulley P ₁₃ once, passed through the idle pulleys a ₃₁ and a _32, and wound around the pulley P ₂₃ once, and the idle pulley a
Through _33, 1.25 lap winding with a pulley P _33, passes through the idle pulley a _34, once-wound with a pulley P _43, passes through the idle pulley a _35, a _36, a pulley P ₅₃ 1.5
It goes around the idle pulley a ₃₇ with a circle, and the pulley P ₆₃
It is wound around once and fixed to the link member L ₆ .

(Wire-4) From the wire-4 drive system, it is wound around the pulley P ₁₄ once, passes through the idle pulleys a ₄₁ and a _42, and is wound around the pulley P ₂₄ once.
After passing through ₄₃ , winding around the pulley P ₃₄ for 1.25 rounds, passing through the idle pulley a ₄₄ , passing around the pulley P ₄₄ once around, passing through the idle pulley a ₄₅ , winding around the pulley P ₅₄ for 1.25 rounds, idle pulley After passing through a ₄₆ , it is wound around the pulley P ₆₄ once and is fixed to the link member L ₆ .

(Wire-5) From the wire-5 drive system, it is wound around the pulley P ₁₅ once, passes through the idle pulleys a ₅₁ and a _52, and is wound once around the pulley P _25.
After passing through _{53, it} is wound around the pulley P ₃₅ for 1.5 turns, passes through the idle pulley a _54, is wound around the pulley P ₄₅ once, and is fixed to the link member L ₄ .

(Wire-6) From the wire-6 drive system, it is wound around the pulley P ₁₆ once, passes through idle pulleys a ₆₁ and a _62, and is wound around the pulley P ₂₆ once, and idle pulley a
After passing through ₆₃ , it winds around the pulley P ₃₆ once, passes through the idle pulley a ₆₄ , winds around the pulley P ₄₆ once, and is fixed to the link member L ₄ .

(Wire-7) From the wire-7 drive system, it is wound around the pulley P ₁₇ once, passed through the idle pulley a ₇₁ , wound around the pulley P ₂₇ once, and fixed to the link member L ₂ .

(Wire-8) From the wire-8 drive system, it is wound around the pulley P ₁₈ once, passed through the idle pulley a ₈₁ , wound around the pulley P ₂₈ once, and fixed to the link member L ₂ .

The torque of each joint J ₁ -J ₇ is detected by the tension differential type torque sensor. As such a tension differential type sensor, a patent application No. 289998 was issued in 1987.
It is possible to use the one indicated by the issue. In the wire interference drive mechanism of the robot arm having such a configuration, the torque of the target joint is controlled by controlling the tension of each wire.

The control of the tension of each wire and the determination of the torque of the target joint are performed as follows. First, the relationship among the tension of the wire, the diameter of the pulley, the joint torque, and the axial force of the joint J ₁ is represented by the following mathematical formula 1.

[0023]

[Equation 1] Here f _i: wire -i tension _{(f i ≧ 0) τ i} : joint J _i of the torque P _1: axial force of the joint J ₁ (all wire - the sum of the tension) A; flop - Li diameter, wire - 8x8 transformation matrix determined by how to multiply

Method for determining tension of each wire 1. The target joint torque τ _ri (i = 1 to 7) is determined. The DCC method, the use of J ^T , and other methods can be used to determine the target joint torque.

2. Formula 2 is calculated.

[Equation 2]

3. Find the smallest f _i . _{min (f i) (i =} 1~8)

4. The target value P _r1 of the axial force of the pulley 1 is _calculated by Equation 3
Ask by.

[Number 3] _{P r1 = -8 · min (f} i)

5. Equation 4 is calculated again, and the target tension f
_ri (i = 1 to 8) is calculated.

[Equation 4] * However, as a simple method, there is also a method of setting P _r1 to a sufficiently large positive value.

6. According to the formula 5, torque servo is performed using the feedback signal τ _si (i = 1 to 8) from each joint tension operation type sensor, and the tension f _ai applied to each wire is calculated.
(I = 1 to 8) is obtained and added by each wire-driving system.

[Equation 5] * However, PID {•} is the joint torque deviation (τ _ri −
τ _si ) (i = 1 to 8) means performing PID control.

[0030]

According to the wire interference drive system of the robot arm of the present invention, the number of wires required is as small as "the smallest even number exceeding n". This makes it possible to manufacture a lightweight, slim, and inexpensive robot arm. Also, the closer the joint is to the base, the more wire it takes. As a result, even if a uniform wire drive system is used, greater torque can be generated at joints closer to the base. In addition, the wire-drive system can be used as a common component. Furthermore, each joint torque can be directly measured by the tension actuated torque sensor arranged near each joint, and the measured joint torque is fed back to the control system to reduce the friction loss of the pulley. The effect of can be removed. Therefore, according to the present invention, it is possible to obtain a wire-interference drive system for a robot arm with good controllability.

[Brief description of drawings]

FIG. 1 is a front explanatory view showing the configuration of a robot arm.

FIG. 2 is a perspective explanatory view of a tension actuated torque sensor.

FIG. 3 is an explanatory perspective view showing paths of all wires.

FIG. 4 is a perspective explanatory view showing a route of a wire-1.

FIG. 5 is a perspective explanatory view showing a route of a wire-2.

FIG. 6 is an explanatory perspective view showing a route of a wire-3.

FIG. 7 is an explanatory perspective view showing a route of a wire-4.

FIG. 8 is an explanatory perspective view showing a route of a wire-5.

FIG. 9 is a perspective explanatory view showing a route of a wire-6.

FIG. 10 is an explanatory perspective view showing a route of a wire-7.

FIG. 11 is an explanatory perspective view showing a route of a wire-8.

[Explanation of symbols]

 1 Robot arm 11 Torque detection sensor W Wire-L Link member J Joint a Idle pulley P pulley A Wire drive system

Claims (1)

[Claims] 1. A wire interference driving method for driving a robot arm having n joints, wherein each joint is provided with pulleys of the same number as the number of wires hanging thereon so that they can rotate independently of each other. Prepare a minimum even number of wires that exceed the number of wires, and wrap the wire that hangs on each joint axis more than one turn around the pulley, then go through that joint axis, and the number of wires that hang on that joint axis is the most proximal When the number of wires that hang on the joint axis next to the joint side is the same, two of the wires that hang on the joint axis are fixed to the link member on the most distal side of the joint axis, and The joint has two wires, the joint at the most proximal end has an even number of wires exceeding n, and the (n-i) th joint from the most proximal end has (i + 1) ) So that the smallest even number of wires over , The number of even-numbered wires on each joint axis should be the total number of wires for forward rotation and wires for backward rotation of the same number, and the tension of each wire should be controlled to achieve the desired torque of the target joint. Interference drive system for robot arm characterized by