Development of an Active Worktable and Its Application to Force Control of Robot Manipulators

2000 ◽  
Vol 12 (3) ◽  
pp. 249-253
Author(s):  
Shin-ichi Nakajima ◽  
Keyword(s):  
Force Control ◽  
Degrees Of Freedom ◽  
Control Method ◽  
Robot Manipulator ◽  
Impedance Control ◽  
Robot Manipulators ◽  
Compliant Motion ◽  
Stiffness Control

An active worktable, which can be applied to force control tasks of commercial robot manipulators, has been designed and built. The active worktable has several degrees of freedom and accommodates its position/force in accordance with the motion of a robot manipulator. A stiffness control method and an impedance control method are implemented in the active worktable to achieve compliant motion. Several experiments were carried out to confirm basic effectiveness of the active worktable.

Educational Force Control Using a Modular 2-DOF Serial Robot Manipulator and Low-Cost 2-DOF Force Sensor

2019 ◽  
Author(s):  
Stephen Mascaro
Keyword(s):  
Force Control ◽  
Degrees Of Freedom ◽  
Hybrid Control ◽  
Robot Manipulator ◽  
Impedance Control ◽  
Low Cost ◽  
Force Sensor ◽  
Physical Contact ◽  
Dynamic Force ◽  
Control Techniques

Abstract This paper describes a modular 2-DOF serial robotic system and accompanying experiments that have been developed to instruct robotics students in the fundamentals of dynamic force control. In prior work, we used this same robot to showcase and compare the performance of a variety of textbook techniques for dynamic motion control (i.e. fast/accurate trajectory tracking using dynamic model-based and robust control techniques). In this paper we now add a low-cost 3D-printed 2-DOF force sensor to this modular robot and demonstrate a variety of force control techniques for use when the robot is in physical contact with the environment. These include stiffness control, impedance control, admittance control, and hybrid position/force control. Each of these various force control schemes can be first simulated and then experimentally implemented using a MATLAB/Simulink real-time interface. The two-degrees of freedom are just enough to demonstrate how the manipulator Jacobian can be used to implement directional impedances in operational space, and to demonstrate how hybrid control can implement position and force control in different axes. This paper will describe the 2-DOF robot system including the custom force sensor, illustrate the various force control methods that can be implemented, and demonstrate sample results from these experiments.

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.

Sliding Mode Impedance and Stiffness Control of a Pneumatic Cylinder

2019 ◽  
Author(s):  
Jonathon E. Slightam ◽  
Eric J. Barth ◽  
Mark L. Nagurka
Keyword(s):  
Motion Control ◽  
Sliding Mode ◽  
Impedance Control ◽  
Pneumatic Cylinder ◽  
Control Methods ◽  
Control Applications ◽  
Compliant Motion ◽  
Simultaneous Control ◽  
Stiffness Control ◽  
Virtual Impedance

Abstract Pneumatic double acting cylinders are able to provide inherent stiffness and force control for compliant motion control applications. Impedance control methods allow for a broad spectrum of mechanical properties of actuators to be achieved. The range of this spectrum can be increased by simultaneously controlling the actuator’s inherent stiffness and impedance, a concept explored in this paper. Presented here is a sliding mode impedance and stiffness controller for a servo-pneumatic double acting cylinder. Two proportional servo-valves are employed for simultaneous control of the virtual impedance and inherent stiffness of the pneumatic cylinder. Experimental results of tracking trajectories and contact are reported and discussed with respect to different approaches in the literature.

Singularity Analysis of Serial Robot-Manipulators

1996 ◽  
Vol 118 (4) ◽  
pp. 520-525 ◽  
Author(s):  
A. Karger
Keyword(s):  
Degrees Of Freedom ◽  
Robot Manipulator ◽  
Robot Manipulators ◽  
Singularity Analysis ◽  
Singular Set ◽  
Singular Configurations ◽  
Special Cases ◽  
Serial Robot ◽  
Singular Configuration ◽  
Actual Configuration

This paper is devoted to the description of the set of all singular configurations of serial robot-manipulators. For 6 degrees of freedom serial robot-manipulators we have developed a theory which allows to describe higher order singularities. By using Lie algebra properties of the screw space we give an algorithm, which determines the degree of a singularity from the knowledge of the actual configuration of axes of the robot-manipulator only. The local shape of the singular set in a neighbourhood of a singular configuration can be determined as well. We also solve the problem of escapement from a singular configuration. For serial robot-manipulators with the number of degrees of freedom different from six we show that up to certain exceptions singular configurations can be avoided by a small change of the motion of the end-effector. We also give an algorithm which allows to determine equations of the singular set for any serial robot-manipulator. We discuss some special cases and give examples of singular sets including PUMA 560.

scholarly journals Analysis and Synthesis of Global Nonlinear H∞ Controller for Robot Manipulators

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Carlos Alberto Chavez Guzmán ◽  
Luis Tupak Aguilar Bustos ◽  
Jován Oseas Mérida Rubio
Keyword(s):  
Lyapunov Function ◽  
Degrees Of Freedom ◽  
Gravitational Force ◽  
Robot Manipulator ◽  
Robot Manipulators ◽  
Global Asymptotical Stability ◽  
Simulation Studies ◽  
External Disturbances ◽  
Analysis And Synthesis ◽  
Force Compensation

The H∞ regulation problem for robot manipulators using gravitational force compensation or precompensation has been solved locally while global asymptotical stability (or global stability) has been demonstrated using other methodologies. A solution to the global nonlinear H∞ regulation problem for l-degrees-of-freedom (l-DOF) robot manipulators, affected by external disturbances, is presented. We showed that the Hamilton-Jacobi-Isaacs (HJI) inequality, inherited in the solution of the H∞ control problem, is satisfied by defining a strict Lyapunov function. The performance issues of the nonlinear H∞ regulator are illustrated in experimental and simulation studies made for a 3-DOF rigid links robot manipulator.

Design and Control of Supporting Arm for Reducing Factory Worker Load With Desired Support Force and Stiffness Characteristics

2016 ◽  
Author(s):  
Tetsuro Miyazaki ◽  
Takuya Iijima ◽  
Kazushi Sanada
Keyword(s):  
Degrees Of Freedom ◽  
Control Method ◽  
Robot Manipulator ◽  
Experimental System ◽  
Factory Worker ◽  
Target Weight ◽  
Support Force ◽  
Stiffness Characteristics ◽  
And Control ◽  
Pneumatic Cylinders

This paper proposes a design and control method of a supporting arm which reduces factory worker load. The supporting arm is a robot manipulator, which is driven by pneumatic cylinders, and is attached to the worker’s hip. In some situation, the factory worker is forced to work with an uncomfortable posture. By using the supporting arm, the worker leg loads are relaxed, and the worker posture is stabilized. To support 50 % weight of the worker, the link system of the supporting arm is designed, and the pneumatic cylinders for actuation are selected. There are two required specifications: (i) support force is sufficient for supporting target load, and (ii) desired stiffness characteristics in the hip height direction can be obtained. The support force is controlled by a two degrees of freedom control system to satisfy the required specifications. An experimental system of the supporting arm was developed, and its performance was evaluated by experiments. As a result, the experimental system shows capability of supporting the target weight and controllability of stiffness.

scholarly journals Aerial Tele-Manipulation with Passive Tool via Parallel Position/Force Control

2021 ◽  
Vol 11 (19) ◽  
pp. 8955
Author(s):  
Mostafa Mohammadi ◽  
Davide Bicego ◽  
Antonio Franchi ◽  
Davide Barcelli ◽  
Domenico Prattichizzo
Keyword(s):  
Contact Interaction ◽  
Force Control ◽  
Degrees Of Freedom ◽  
Haptic Feedback ◽  
Situational Awareness ◽  
Control Method ◽  
Bilateral Teleoperation ◽  
Compliant Structure ◽  
Rotational Degrees Of Freedom ◽  
Remote Sites

This paper addresses the problem of unilateral contact interaction by an under-actuated quadrotor UAV equipped with a passive tool in a bilateral teleoperation scheme. To solve the challenging control problem of force regulation in contact interaction while maintaining flight stability and keeping the contact, we use a parallel position/force control method, commensurate to the system dynamics and constraints in which using the compliant structure of the end-effector the rotational degrees of freedom are also utilized to attain a broader range of feasible forces. In a bilateral teleoperation framework, the proposed control method regulates the aerial manipulator position in free flight and the applied force in contact interaction. On the master side, the human operator is provided with force haptic feedback to enhance his/her situational awareness. The validity of the theory and efficacy of the solution are shown by experimental results. This control architecture, integrated with a suitable perception/localization pipeline, could be used to perform outdoor aerial teleoperation tasks in hazardous and/or remote sites of interest.

Theory and Experiments on the Compliance Control of Redundant Robot Manipulators

1990 ◽  
Vol 112 (4) ◽  
pp. 653-660 ◽  
Author(s):  
H. Kazerooni ◽  
K. G. Bouklas ◽  
J. Guo
Keyword(s):  
Degrees Of Freedom ◽  
Control Method ◽  
Robot Manipulators ◽  
Industrial Robot ◽  
Redundant Robot ◽  
Control Approach ◽  
Six Degrees Of Freedom ◽  
The Stability ◽  
Control Methodology ◽  
Theory And Experiments

This work presents a control methodology for compliant motion in redundant robot manipulators. This control approach takes advantage of the redundancy in the robot’s degrees of freedom: while a maximum six degrees of freedom of the robot control the robot’s endpoint position, the remaining degrees of freedom impose an appropriate force on the environment. To verify the applicability of this control method, an active end-effector is mounted on an industrial robot to generate redundancy in the degrees of freedom. A set of experiments are described to demonstrate the use of this control method in constrained maneuvers. The stability of the robot and the environment is analyzed.

Linearized Dynamic Models for Robot Manipulators With Varying Link Parameters

1991 ◽  
Author(s):  
Chang-Jin Li ◽  
T. S. Sankar ◽  
A. Hemami
Keyword(s):  
Computational Complexity ◽  
Degrees Of Freedom ◽  
Dynamic Models ◽  
Robot Manipulator ◽  
Robot Manipulators ◽  
Mechanical Systems ◽  
Computational Algorithms ◽  
Inverse Dynamic ◽  
Dynamic Link

Abstract In this paper, two fast computational algorithms are developed for effective formulation for the linearized dynamic robot models with varying (kinematic and dynamic) link parameters. The proposed algorithms can generate complete linearized (inverse) dynamic models for robot manipulators, taking variations (e.g., inexactness, inconstancy, or uncertainty) of the kinematic and dynamic link parameters into account. They can be applied to any robot manipulator with rotational and/or translational joints, and can be utilized, also, for sensivitity analysis of similar mechanical systems. The computational complexity of these algorithms is only of order O(n), where n is the number of degrees-of-freedom of the robot manipulator.

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