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Robot Arm Kinematics, Dynamics, and Control

IP.com Disclosure Number: IPCOM000131565D
Original Publication Date: 1982-Dec-01
Included in the Prior Art Database: 2005-Nov-11

Publishing Venue

Software Patent Institute

Related People

C. S. George Lee: AUTHOR [+3]

Abstract

University of Michigan, Ann Arbor Behind every robotic movement is a series of complex geometric evaluations and equations that describe motion dynamics. Conformance to system goals must also be considered. An industrial robot is a general-purpose manipulator that consists of several rigid bodies, called links, connected in series by revolute or prismatic joints (Figure I ). One end of the chain is attached to a supporting base, while the other end is free and equipped with a tool to manipulate objects or perform assembly tasks. The motion of the joints results in relative motion of the links. Mechanically, a robot is composed of an arm (or primary frame) and a wrist subassembly plus a tool and is designed to reach a workpiece located within its work volume. The work volume is a sphere of influence for a robot whose arm can deliver the wrist subassembly unit to any point within the sphere. The arm subassembly typically consists of three degree-of-freedom movements, which together place or position the wrist unit at the workpiece. The wrist subassembly unit usually consists of three rotary motions, often called pitch, yaw, and roll, and their combination orients the tool according to the configuration of the object to ease pickup. Hence for a six joint robot, the arm subassembly is the positioning mechanism, while the wrist subassembly is the orientation mechanism.

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Robot Arm Kinematics, Dynamics, and Control

C. S. George Lee,

University of Michigan, Ann Arbor

Behind every robotic movement is a series of complex geometric evaluations and equations that describe motion dynamics. Conformance to system goals must also be considered.

An industrial robot is a general-purpose manipulator that consists of several rigid bodies, called links, connected in series by revolute or prismatic joints (Figure I ). One end of the chain is attached to a supporting base, while the other end is free and equipped with a tool to manipulate objects or perform assembly tasks. The motion of the joints results in relative motion of the links. Mechanically, a robot is composed of an arm (or primary frame) and a wrist subassembly plus a tool and is designed to reach a workpiece located within its work volume. The work volume is a sphere of influence for a robot whose arm can deliver the wrist subassembly unit to any point within the sphere. The arm subassembly typically consists of three degree-of-freedom movements, which together place or position the wrist unit at the workpiece. The wrist subassembly unit usually consists of three rotary motions, often called pitch, yaw, and roll, and their combination orients the tool according to the configuration of the object to ease pickup. Hence for a six joint robot, the arm subassembly is the positioning mechanism, while the wrist subassembly is the orientation mechanism.

Many commercially available industrial robots are widely used in simple material handling, spot/arc welding, and parts assembly, including the Unimate 2000B and PUMA 260/550/560 series robots by Unimation Inc.; the T3 by Cincinnati Milacron; the Versatran by Prab; the Asea robot; and the Sigma by Olivetti of Italy. These robots, which exhibit their characteristics in motion and geometry, fall into one of four basic motiondefining categories (Figure 1):

Cartesian coordinate (three linear axes),

cylindrical coordinate (two linear and one rotary axes),

spherical or polar coordinate (one linear and two rotary axes). and

revolute or articulated coordinate (three rotary axes).

Most automated manufacturing tasks are done by special- purpose machines that are designed to perform prespecified functions in a manufacturing process. The inflexibility of these machines makes the computer-controlled manipulators more attractive and cost-effective in various manufacturing and assembly tasks. Today's industrial robots, though controlled by mini- /microcomputer, are basically simple positional machines. They...