Five axis direct-drive mini-robot having fifth actuator located at non-adjacent joint

• US 5,528,955 A
• Filed: 09/08/1994
• Issued: 06/25/1996
• Est. Priority Date: 09/08/1994
• Status: Expired due to Fees

• Current Assignee: University of Washington
• Original Assignee: University of Washington
• Inventors: Hannaford, Blake, Moreyra, Manuel R., Marbot, Pierre-Henry M. J.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Kim, Chong H.
• Application Number:
  US08/302,564
• Time in Patent Office: 656 Days
• Field of Search: 74/490.01, 74/490.03, 74/490.04, 901/15, 901/21, 901/23, 414/729, 318/568.1, 318/567.2, 318/569.21
• US Class Current: 74/490.01
• CPC Class Codes: B25J 19/002 using counterweights
• CPC Class Codes: B25J 9/047 the pivoting axis of the first arm being offset to the vertical axis
• CPC Class Codes: B25J 9/06 characterised by multi-articulated arms
• CPC Class Codes: Y10T 74/20305 Robotic arm
• CPC Class Codes: Y10T 74/20317 including electric motor
• CPC Class Codes: Y10T 74/20323 including flaccid drive element

Abstract

A substantially balanced, five-axis, direct drive mini-robot provides repeatable micro-manipulation to micron precision. Dynamic forces of each link are nearly decoupled from the dynamic forces of remaining links. The robot is generally formed as a shoulder, arm and wrist assembly. At the shoulder a linear actuator drives the robot in a linear horizontal movement along a first axis (e.g., z axis). Two additional actuators at the shoulder provide revolute motion to rotate the arm in an xz plane (e.g., for lateral motion) and a yz plane (e.g., for vertical motion), respectively. A fourth actuator provides rotational motion to move an end-effector (manipulator) at the wrist through a yaw motion. A fifth actuator, positioned at the shoulder and linked to the wrist, provides rotational motion to move the end-effector through a pitch motion.

Claims

1. A mini-robot apparatus, comprising five joints respectively connected by first, second, third and fourth links in a kinematic chain, each joint movable in one degree of freedom, the first four joints in the chain directly driven by four respective actuators, the last joint in the chain indirectly driven by a fifth actuator positioned at a non-adjacent link;

and in which the kinematic chain is formed by a shoulder assembly, arm assembly and wrist assembly which together have a center of gravity in vicinity of the shoulder assembly;

the shoulder assembly comprising the first link, second link and third link and a first actuator, second actuator and third actuator, the first actuator for directly driving manipulation of said first joint to define a first degree of freedom, the second actuator directly driving manipulation of said second joint to define a second degree of freedom, the third actuator for directly driving manipulation of the third joint to define a third degree of freedom;

the arm assembly comprising a fourth link and a fourth actuator, the fourth actuator for directly driving the wrist assembly to rotate, said rotation of the wrist assembly defining a fourth degree of freedom;

the wrist assembly comprising a first pulley having a fixed orientation relative to the wrist assembly;

the shoulder assembly further comprising the fifth actuator and a second pulley, the second pulley having a fixed orientation at the shoulder assembly relative to the third link, the second pulley having a drive axis coaxial with a drive axis of the third actuator, the first and second pulley mechanically coupled by an elastic drive belt, the fifth actuator driving the wrist assembly relative to the arm assembly via the pulleys and belt to define a fifth degree of freedom, wherein length of the drive belt varies as the first pulley and wrist assembly rotate relative to the second pulley and the shoulder assembly.

2. The mini-robot apparatus of claim 1, in which origins of the first and second joints intersect along a common axis, and in which origin of the third joint is slightly offset from said common axis.

3. The mini-robot of claim 1, in which dynamic forces in a fourth link coupling the fourth and fifth joints are substantially decoupled from dynamic forces in the remaining three links.

11. The mini-robot of claim 1, in which an axis of rotation of said second pulley is coaxial to an axis of rotation of a shaft driven by said third actuator to minimize twisting forces at the wrists assembly during motions driven by said third actuator.

12. The mini-robot of claim 11, in which the arm assembly further comprises an elongated shaft coupling the fourth actuator to the wrist assembly, the fourth actuator located near the shoulder assembly and driving the shaft to directly couple motion to said wrist assembly.

4. A mini-robot apparatus, comprising:

a shoulder assembly, arm assembly and wrist assembly and having a center of gravity in vicinity of the shoulder assembly wherein the arm assembly is mechanically coupled to the shoulder assembly and the wrist assembly is mechanically coupled to the arm assembly;

the shoulder assembly comprising a first actuator and second actuator for directly driving manipulation of the shoulder assembly in two degrees of freedom, respectively, and a third actuator for directly driving cantilever vertical rotation of the arm assembly in one degree of freedom relative to a joint coupling the arm assembly to the shoulder assembly;

the arm assembly comprising an elongated shaft and a fourth actuator, the fourth actuator for directly driving the wrist assembly in one degree of freedom, the fourth actuator mechanically coupled to one end of the shaft and the wrist assembly mechanically coupled to an opposing end of the shaft, the joint coupling the arm assembly and shoulder assembly being located between said one end and opposing end of the shaft;

the wrist assembly comprising a first pulley;

the shoulder assembly further comprising a fifth actuator and a second pulley, the second pulley having a drive axis coaxial with a drive axis of the third actuator, the first and second pulley mechanically coupled by a drive belt, the fifth actuator driving the wrist assembly relative to the arm assembly via the pulleys and belt in one degree of freedom.

5. The mini-robot of claim 4, in which the shoulder assembly, arm assembly and wrist assembly together form five joints including said coupling joint, said five joints connected by four links in a kinematic chain, each joint movable in one of said five degrees of freedom, the first four joints in the chain directly driven by said first, second, third and fourth actuators, respectively, the fifth joint indirectly driven by said fifth actuator positioned at a non-adjacent link.

6. The mini-robot of claim 4, in which an axis of rotation of said second pulley is coaxial to an axis of rotation of a shaft driven by said third actuator to minimize twisting forces at the wrist assembly during motions driven by said third actuator.

7. A mini-robot apparatus, comprising:

a shoulder assembly, arm assembly and wrist assembly together forming five joints connected by four links in a kinematic chain, each joint movable in one degree of freedom, the apparatus having a center of gravity in vicinity of the shoulder assembly, the arm assembly being mechanically coupled to the shoulder assembly at a third joint of the five joints and the wrist assembly being mechanically coupled to the arm assembly at a fourth joint of the five joints;

the shoulder assembly comprising a first actuator and a second actuator for directly driving manipulation, respectively, of a first and a second joint in said chain, and a third actuator for directly driving a cantilever vertical rotation of the arm assembly at the third joint;

the arm assembly comprising an elongated shaft and a fourth actuator, the fourth actuator for directly driving the fourth joint in said chain, the fourth actuator mechanically coupled to one end of the shaft and the wrist assembly mechanically coupled to an opposing end of the shaft, the fourth joint being located between said one end and opposing end of the shaft;

the wrist assembly comprising a first pulley having a fixed orientation relative to the wrist assembly for linking motion to a fifth joint in said chain;

the shoulder assembly further comprising a fifth actuator and a second pulley, the second pulley having a fixed orientation relative to a third link of the four links, the third link located at the shoulder assembly and a drive axis coaxial with a drive axis Of the third actuator, the first and second pulley mechanically coupled by an elastic drive belt, the fifth actuator driving motion of the wrist assembly relative to the arm assembly via the pulleys and belt, the fifth actuator being located at a non-adjacent link to said fifth joint in the kinematic chain, and wherein length of the belt varies as the first pulley and wrist assembly rotate relative to the second pulley and shoulder assembly.

8. The mini-robot apparatus of claim 7, in which origins of the first and second joints intersect along a common axis, and in which origin of the third joint is slightly offset from said common axis.

9. The mini-robot of claim 7, in which dynamic forces in a fourth link coupling the fourth and fifth joints are substantially decoupled from dynamic forces in the remaining three links.

10. The mini-robot of claim 7, in which an axis of rotation of said second pulley is coaxial to an axis of rotation of a shaft driven by said third actuator to minimize twisting forces at the wrist assembly during motions driven by said third actuator.