Smart Actuator Positioning and Displacement Transmissibility in Serial and Parallel Robot Manipulators for Performance Enhancement

2004 ◽  
Vol 127 (4) ◽  
pp. 589-595 ◽  
Author(s):  
J. Rastegar ◽  
L. Yuan ◽  
J. Zhang
Keyword(s):  
Smart Materials ◽  
Performance Enhancement ◽  
Robot Manipulator ◽  
Robot Manipulators ◽  
High Harmonic ◽  
Harmonic Component ◽  
Operating Speed ◽  
End Effector ◽  
High Harmonics ◽  
Joint Motions

A method is presented for the evaluation of the transmissibility of displacement from smart (active) actuators integrated in the structure of robot manipulators to the manipulator joint and end-effector displacements. The method is based on studying the characteristics of the Jacobian of the mapping function between the two displacements for a given position of the robot manipulator. The developed method provides a tool for the determination of the positioning of smart actuators to provide maximum effectiveness in eliminating high harmonics of the joint or the end-effector motion. In robots with serial and parallel kinematics chains containing nonprismatic joints, due to the associated kinematics nonlinearity, if the joint motions were synthesized with low harmonic trajectories, the end-effector trajectory would still contain high harmonics of the joint motions. Alternatively, if the end-effector motion were synthesized with low harmonic components, due to the inverse kinematics nonlinearity, the actuated joint trajectories would contain a significant high harmonic component. As a result, the operating speed and tracking precision are degraded. By integrating smart materials based actuators in the structure of robot manipulators to provide small amplitude and high frequency motions, the high harmonic component of the actuated joint and/or the end-effector motions can be significantly reduced, thereby making it possible to achieve higher operating speed and tracking precision.

Optimal Integration of Smart Actuators in the Structure of Serial and Parallel Robot Manipulators to Enhance Speed and Tracking Precision

2003 ◽  
Author(s):  
J. Rastegar ◽  
L. Yuan ◽  
J. Zhang
Keyword(s):  
Robot Manipulator ◽  
Robot Manipulators ◽  
High Harmonic ◽  
Harmonic Component ◽  
Optimal Placement ◽  
Operating Speed ◽  
End Effector ◽  
High Harmonics ◽  
Smart Actuators ◽  
Joint Motions

A method to determine optimal placement of smart (active) materials based actuators in the structure of robot manipulators for the purpose of achieving higher operating speed and tracking precision is developed. The method is based on the evaluation of the transmissibility of the displacement from the integrated smart actuators to the robot manipulator joint and end-effector displacements. By studying the characteristics of the Jacobian of the mapping function between the two displacements for a given position of the robot manipulator, the optimal positioning of the smart actuators that provides maximum effectiveness in eliminating high harmonics of the joint motion or the end-effector motion is determined. In robots with serial and parallel kinematics chains containing non-prismatic joints, due to their associated kinematics nonlinearity, if the joint motions were synthesized with low harmonic trajectories, the end-effector trajectory would contain high harmonics of the joint motions. Alternatively, if the end-effector motion were synthesized with low harmonic motions, due to the inverse kinematics nonlinearity, the actuated joint trajectories would contain a significant high harmonic component. As the result, the operating speed and tracking precision are degraded. By integrating smart materials based actuators in the structure of robot manipulators to provide small amplitude and higher frequency motions, the high harmonic component of the actuated joint and/or the end-effector motions are eliminated. As the result, higher operating speed and tracking precision can be achieved.

Micro/Macro or Link-Integrated Micro-actuator Manipulation—A Kinematics and Dynamics Perspective

2006 ◽  
Vol 129 (10) ◽  
pp. 1086-1093 ◽  
Author(s):  
J. Zhang ◽  
J. Rastegar
Keyword(s):  
Dynamic Response ◽  
Closed Loop ◽  
Robot Manipulator ◽  
Robot Manipulators ◽  
High Harmonic ◽  
Kinematics And Dynamics ◽  
Control Problems ◽  
End Effector ◽  
Micro Actuators ◽  
And Control

Smart (active) materials based actuators, hereinafter called micro-actuators, have been shown to be well suited for the elimination of high harmonics in joint and/or end-effector motions of robot manipulators and in the reduction of actuator dynamic response requirements. Low harmonic joint and end-effector motions, as well as low actuator dynamic response requirements, are essential for a robot manipulator to achieve high operating speed and precision with minimal vibration and control problems. Micro-actuators may be positioned at the end-effector to obtain a micro- and macro-robot manipulation configuration. Alternatively, micro-actuators may be integrated into the structure of the links to vary their kinematics parameters, such as their lengths during the motion. In this paper, the kinematics and dynamics consequences of each of the aforementioned alternative are studied for manipulators with serial and closed-loop chains. It is shown that for robot manipulators constructed with closed-loop chains, the high harmonic components of all joint motions can be eliminated only when micro-actuators are integrated into the structure of the closed-loop chain links. The latter configuration is also shown to have dynamics advantage over micro- and macro-manipulator configuration by reducing the potential vibration and control problems at high operating speeds. The conclusions reached in this study also apply to closed-loop chains of parallel and cooperating robot manipulators.

Optimal Integration of Smart Actuators in Parallel and Cooperating Robots to Enhance Operating Speed and Accuracy

2001 ◽  
Author(s):  
L. Yuan ◽  
J. Rastegar
Keyword(s):  
Robot Manipulators ◽  
High Harmonic ◽  
Control Problems ◽  
Operating Speed ◽  
Parallel Kinematics ◽  
Optimal Integration ◽  
Highly Nonlinear ◽  
Cooperating Robots ◽  
Harmonic Components ◽  
Joint Motions

Abstract Robot manipulators with parallel kinematics chains and two or more robots manipulating an object form closed kinematics chains. When revolute joints are used in the construction of such robotic manipulation systems, the presence of closed chains and their associated kinematics nonlinearity demands high harmonic motions in at least a number of the actuated joints. This is the case even if all the links are relatively rigid and attempt is made to synthesize the joint motions with minimal harmonic content. The presence of high harmonic components in the actuated joint motions is undesirable since as the operating speed is increased, their frequencies would rapidly increase and move beyond the dynamic response limitations of the actuating drives, thereby causing vibration and control problems. The performance of the system in terms of cycle time, tracking precision and the like would therefore suffer. This is particularly the case since the dynamics of such systems is also highly nonlinear and require higher harmonic components in the actuating torques (forces). In this paper, a systematic method is presented for optimal integration of smart (active) materials based actuators into the structure of cooperating robots and robot manipulators with parallel kinematics chain for the purpose of eliminating the high harmonic components of their actuated joint motions. As the result, the potential excitation of the natural modes of vibration of such systems and their related control problems can be greatly reduced. The resulting robotic systems should therefore be capable of operating at higher speeds with increased precision.

Integration of Smart Actuators in the Structure of Robots for High-Speed and Precision Object Manipulation

2001 ◽  
Author(s):  
Jahangir S. Rastegar ◽  
Lifang Yuan
Keyword(s):  
High Speed ◽  
Robot Manipulator ◽  
Robot Manipulators ◽  
High Harmonic ◽  
Object Manipulation ◽  
Smart Actuators ◽  
Computer Controlled ◽  
Harmonic Components ◽  
Joint Motions ◽  
And Control

Abstract A systematic method is presented for optimal integration of smart actuators into the structure of robot manipulators for the purpose of enabling them to perform smooth object manipulation with smooth actuated joint motions. Here, the motions are considered to be smooth if they do not contain high harmonic components. For optimal positioning of smart actuators in the structure of robot manipulators, a method is developed based on the evaluation of the transmissibility of displacement (velocity and/or force) from the smart actuators to the robot manipulator joint motions and the end-effector displacements (velocity and/or force). A method is then presented for synthesizing actuated joint and object motions to achieve trajectories that do not contain high harmonic components. By minimizing the high harmonic components of the required joint and object motions with properly sized and placed smart actuators, such computer-controlled machines can operate at relatively higher speeds and achieve greater tracking precision with minimal vibration and control problems. A number of numerical examples are provided.

Optimal Smart Actuator Integration to Reduce Vibration in High Speed Mechanical Systems

2001 ◽  
Author(s):  
J. Rastegar ◽  
L. Yuan ◽  
L. Hua
Keyword(s):  
High Speed ◽  
Robot Manipulator ◽  
Robot Manipulators ◽  
High Harmonic ◽  
Smart Actuators ◽  
Computer Controlled ◽  
Harmonic Components ◽  
Smart Actuator ◽  
Joint Motions ◽  
And Control

Abstract A systematic method is presented for optimal integration of smart actuators into the structure of robot manipulators for the purpose of enabling them to perform smooth object manipulation with smooth actuated joint motions. Here, the motions are considered to be smooth if they do not contain high harmonic components. For optimal positioning of smart actuators in the structure of robot manipulators, a method is developed based on the evaluation of the transmissibility of displacement (velocity and/or force) from the smart actuators to the robot manipulator joint motions and the end-effector displacements (velocity and/or force). A method is then presented for synthesizing actuated joint and object motions to achieve trajectories that do not contain high harmonic components. By minimizing the high harmonic components of the required joint and object motions with properly sized and placed smart actuators, such computer-controlled machines can operate at relatively higher speeds and achieve greater tracking precision with minimal vibration and control problems. A number of numerical examples are provided.

Trajectory Synthesis and Redundancy Resolution for High Speed Point to Point Motions of Redundant Robot Manipulators

1997 ◽  
Author(s):  
W. Kim ◽  
J. Rastegar
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Robot Manipulator ◽  
Robot Manipulators ◽  
Dynamic Performance ◽  
High Harmonic ◽  
Harmonic Excitation ◽  
Redundancy Resolution ◽  
Tracking Accuracy ◽  
Point To Point

Abstract Trajectory synthesis for robot manipulators with redundant kinematic degrees-of-freedom has been studied by numerous investigators. Redundant manipulators are of interest since the redundant degrees-of-freedom can be used to improve the local and global kinematic and dynamic performance of a system. As a robot manipulator is forced to track a given trajectory, the required actuating torques (forces) may excite the natural modes of vibration of the system. Noting that manipulators with revolute joints have nonlinear dynamics, high harmonic excitation torques are generally generated even though such harmonics have been eliminated from the synthesized trajectories and filtered from the drive inputs. In this paper, a redundancy resolution method is developed based on the Trajectory Pattern Method (TPM) to synthesize trajectories such that the actuating torques required to realize them do not contain higher harmonic components with significant amplitudes. With such trajectories, a robot manipulator can operate at higher speeds and achieve higher tracking accuracy with suppressed residual vibration. As an example, optimal trajectories are synthesized for point to point motions of a plane 3R manipulator.

On the Effects of the Operating Speed on the Dynamic Behavior of Manipulators With Rigid Links

1992 ◽  
Author(s):  
Q. Tu ◽  
Jahangir Rastegar
Keyword(s):  
Energy Transfer ◽  
Total Energy ◽  
Dynamic Behavior ◽  
Robot Manipulator ◽  
Robot Manipulators ◽  
Vibrational Excitation ◽  
Operating Speed ◽  
Higher Harmonics ◽  
Resonant Energy ◽  
Resonant Energy Transfer

Abstract The effect of tile operating speed on the dynamic behavior of robot manipulators is determined by examining the potential resonant energy transfer to a robot manipulator system during its motion by the different harmonics of the actuating torques (forces). The potential resonant energy transfer (hereafter called the energy transfer), particularly by the higher harmonics present in the actuating torques, is of considerable interest since they represent one of the main sources of vibration and control problems in such systems. For a given trajectory pattern, the ratios of the total energy transfer by the non-trajectory and the “higher” harmonics of the actuating torques to the total energy input to the system are determined. Here, the higher harmonics refers to the harmonics with frequencies above the highest frequency of the trajectory harmonics. It is shown that in the absence of gravity, for the class of nonlinear dynamics systems represented by the rigid link robot manipulators, the ratios are independent of the speed of operation. For a given path geometry, the relative magnitude of the individual energy transfer is, however, dependent on the positioning of the path within the workspace of the manipulator and the pattern of motion. In the presence of gravity, as the operating speed is increased, the ratios tend to their no gravity values. The application of the developed method to manipulator synthesis and path and trajectory planning for minimal system susceptibility to vibrational excitation, and a number of related topics of interest are discussed.

A Systematic Method for Optimal Integration of Smart Materials Into the Structure of High Speed Mechanisms

1999 ◽  
Author(s):  
L. Yuan ◽  
J. Rastegar
Keyword(s):  
Smart Materials ◽  
High Speed ◽  
Closed Loop ◽  
Vibrational Excitation ◽  
High Harmonic ◽  
Harmonic Component ◽  
Primary Source ◽  
Linkage Mechanism ◽  
Constant Input ◽  
Systematic Method

Abstract A systematic method is presented for the integration of smart (active) materials based actuators into the structure of mechanical systems in general and mechanisms with closed-loop chains in particular for the purpose of modifying the output motion of the system. In the resent study, the method is applied to a four-bar linkage mechanism with a constant input velocity for the purpose of eliminating the high harmonic component of the output link motion. By eliminating the high harmonic component of the output motion of a mechanism, the potential vibrational excitation that the mechanism can impart on the overall system and its own structure is greatly reduced. The resulting system should therefore be capable of operating at higher speeds with increased precision. For mechanisms with rigid links, the primary source of high harmonic motions is the nonlinearity of the kinematics of the closed-loop chain. The usually less prominent high harmonic motions due to joint and/or structural flexibility may be eliminated in a similar manner and will be addressed in future publications.

A Systematic Method for Kinematics Synthesis of High-Speed Mechanisms With Optimally Integrated Smart Materials

2000 ◽  
Author(s):  
J. Rastegar ◽  
L. Yuan
Keyword(s):  
Smart Materials ◽  
High Speed ◽  
Vibrational Excitation ◽  
High Harmonic ◽  
Harmonic Component ◽  
Linkage Mechanism ◽  
Output Link ◽  
Mechanism Synthesis ◽  
Systematic Method ◽  
Four Bar Linkage

Abstract A systematic method is presented for kinematics synthesis of high-speed mechanisms with optimally integrated smart materials based actuators for the purpose of modifying the output link motion. As an example, the method is applied to a four-bar linkage mechanism that is synthesized for function generation to eliminate the high harmonic component of the output link motion. For mechanisms with rigid links, the high harmonic motions are generated due to the nonlinearity of the kinematics of their closed-loop chains. By eliminating the high harmonic component of the output motion, the potential vibrational excitation that the mechanism can impart on the overall system and its own structure is greatly reduced. The resulting system should therefore be capable of operating at higher speeds with increased precision. A numerical example is provided together with a discussion of the application of the method to other mechanism synthesis problems and some related topics of interest.

Dynamical Resolution of Redundancy for Robot Manipulators

1993 ◽  
Vol 115 (3) ◽  
pp. 592-598 ◽  
Author(s):  
A. Ghosal ◽  
S. Desa
Keyword(s):  
Large Class ◽  
Robot Manipulator ◽  
Robot Manipulators ◽  
Dynamic State ◽  
Redundancy Resolution ◽  
End Effector ◽  
Dynamical Approach ◽  
Pseudo Inverse

A large class of work in the robot manipulator literature deals with the kinematical resolution of redundancy based on the pseudo-inverse of the manipulator Jacobian. In this paper an alternative dynamical approach to redundancy resolution is developed which utilizes the mapping between the actuator torques and the acceleration of the end-effector, at a given dynamic state of the manipulator. The potential advantages of the approach are discussed and an example of a planar 3R manipulator following a circular end-effector trajectory is used to illustrate the proposed approach as well as to compare it with the more well-known approach based on the pseudo-inverse.

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