ROBOTIC IMPEDANCE CONSTRAINTS FOR HAPTIC FEEDBACK (original) (raw)

Constraint Coupling of Force and Motion Between Real and Virtual Mechanisms.

In the approach presented in this research, a six DOF industrial manipulator is used as the master device to provide haptic feedback to the operator. In order develop effective constraints between the motion of the slave and master, a virtual manipulator concept is developed that couples the actual robotic kinematics with the constraints of the simulated slave manipulator. The position and velocity errors between the actual and virtual mechanisms are used to develop an optimal impedance controller that constrains the motion of the master in all directions that are orthogonal to the allowable motions of the slave. This approach allows the use of a conventional industrial manipulator as an effective haptic display device.

Haptic Force Control Based on Impedance/Admittance Control

IFAC Proceedings Volumes, 2005

There are two popular control methods widely used in haptic controller design. First, is impedance control-the operator motion input is measured, and then, the reaction force is fed back to the operator. The alternative method is admittance controlforces exerted by operator are measured and positions are fed back to the operator. Both, impedance and admittance control are also two basic methods for interacting with a virtual environment. In this paper, several experiments were performed to evaluate the suitability of impedance control with force feedback for haptic interface development. The difference between conventional application of impedance control in robot motion control and its application in haptic interface development is investigated. Open loop impedance control methodology is implemented for static case and a general-purpose robot under open loop impedance control was developed as a haptic device, while a closed loop model based impedance control was used for haptic controller design in both static and dynamic case. The factors that could affect to the performance of a haptic interface are also investigated experimentally using parametric studies. The experiments were carried out using an experimental setup. Experimental results for 1 DOF rotational motion and 2 DOF planar translational motion systems are presented. Other experimental results are also shown and discussed.

Haptic force control based on impedance/admittance control aided by visual feedback

Multimedia Tools and Applications, 2008

There are two popular control methods widely used in haptic controller design. First, is impedance control -the operator motion input is measured, and then, the reaction force is fed back to the operator. The alternative method is admittance controlforces exerted by operator are measured and positions are fed back to the operator. Both, impedance and admittance control are also two basic methods for interacting with a virtual environment. In this paper, several experiments were performed to evaluate the suitability of impedance control with force feedback for haptic interface development. The difference between conventional application of impedance control in robot motion control and its application in haptic interface development is investigated. Open loop impedance control methodology is implemented for static case and a general-purpose robot under open loop impedance control was developed as a haptic device, while a closed loop model based impedance control was used for haptic controller design in both static and dynamic case. The factors that could affect to the performance of a haptic interface are also investigated experimentally using parametric studies. The experiments were carried out using an experimental setup. Experimental results for 1 DOF rotational motion and 2 DOF planar translational motion systems are presented. Other experimental results are also shown and discussed.

Adaptive impedance control of a haptic interface

Mechatronics, 2004

Teleoperation enables an operator to manipulate remote objects. One of the main goals in teleoperation research is to provide the operator with the feeling of the telepresent object and of being present at the remote site. In order for this to happen, a master robot must be designed as a bilateral control system that can transmit position commands to a slave robot and reflect the interaction force. A newly proposed adaptive impedance algorithm is applied to the force control of a haptic interface that has been developed as a master robot. With the movement of the haptic interface for position command generation, the impedance between an operator and the haptic interface varies dynamically. When the impedance parameters and the dynamics of the haptic interface are known precisely, many model based control theories and methods can be used to control the interface accurately. However, due to the parametersÕ variations and the uncertainty in the dynamic model, it is difficult to control the interface precisely. Therefore, this paper proposes a new adaptive impedance control algorithm and experimentally verifies the effectiveness of the algorithm for control of the haptic interface.

The haptic impendance control through virtual environment force compensation

2011

This paper presents force-position haptic control methods used to increase trajectory tracking accuracy through the compensation on two axes depending on the forces from a virtual environment. Kinematic structure of the haptic device is analyzed, the end-effector trajectory control loop is modeled using an impedance control function and, in order to eliminate singularities and areas of instability, the real-time control system architecture is designed by direct and inverse kinematic computing using transposed Jacobian matrix instead of inverse matrix computing. A testing and simulation diagram was developed for control system modeling in SIMULINK, using signal generators that are designed to replace the haptic device and virtual interface. To simplify the control scheme the force feedback to the human operator was dropped. The results yielded by the impedance hybrid force position control system have revealed the position compensation when a force is received from the virtual enviro...

The Command of a Virtual Industrial Robot Using a Dedicated Haptic Interface

Advanced Materials Research, 2013

In this paper is presented a study regarding the possibilities of commandinga virtual robot using a haptic interface. In order to demonstrate the functionality of this concept, a dedicated device with 1 DOF was developed. This device consists of twin motor-gearbox able to acquire and transmit the angular data of the shaft and return a haptic feedback corresponding to the robot movement. The proposed haptic device makes it possible to command one joint of an industrial robot and can be used as an essential component for the development of an exoskeleton for human arm and is able to generate a haptic interaction for all the joints. The exoskeleton solution will allow a structural similarity between the haptic device and an articulated robot arm. The test results with haptic feedback scenarios show that the proposed system can help inexperienced users to handle robot operation and programming tasks in an intuitive way.

Experimental evaluation of haptic control for human activated command devices

Haptics refers to a widespread area of research that focuses on the interaction between humans and machine interfaces as applied to the sense of touch. A haptic interface is designed to increase the realism of tactile and kinesthetic sensations in applications such as virtual reality, teleoperation, and other scenarios where situational awareness is considered important, if not vital. This paper investigates the use of electric actuators and non-linear algorithms to provide force feedback to an input command device for providing haptics to the human operator. In particular, this work involves the study and implementation of a special case of feedback linearization known as inverse dynamics control and several outer loop impedance control topologies. It also investigates the issues concerned with force sensing and the application of model based controller functions in order to vary the desired inertia and the desired mass matrix. Results of the controllers’ abilities to display any desired impedance and provide the required kinesthetic constraint of virtual environments are shown on two experimental test rigs designed for this purpose.

Design and implementation of haptic interactions

Ph.D. Thesis of Naci Zafer, 2000 , 2000

This thesis addresses current haptic display technology where the user interacts with a virtual environment by means of specialized interface devices. The user manipulates computer generated virtual objects and is able to feel the sense of touch through haptic feedback. The objective of this work is to design high performance haptic interactions by developing multi-purpose virtual tools and new control schemes to implement a PUMA 560 robotic manipulator as the haptic interface device. This study focuses on engineering applications where the interaction is with computer generated physical models of dynamic systems and mechanisms. Thus, the research presented in this dissertation focuses on introducing and using new modeling techniques in designing haptic interactions. The interactions are modeled by coupling the motions of the virtual tool with those of the PUMA 560 robotic manipulator. Kane’s method is introduced to model dynamics of virtual tools. The resulting model is used to develop an approach to dynamic simulation for use in interacting haptic display, which includes multibody systems switching constraints. Multibody dynamics of a virtual simulator, a dumbbell, is developed and the advantages of the Kane’s method in handling the non-holonomic constraints are presented. Experimental data is also collected to show various contact configurations. A two-degree of freedom virtual manipulator is modeled to feel the surface of a taurus shape. An optimal position controller is designed to achieve stable interactions. The controller is designed to achieve kinematic coupling between the virtual manipulator and the haptic display device to impose motion constraints and the virtual interactions. Stability of the haptic interface is also studied and proved using Lyapunov’s direct method. Experimental data in various positions of the robotic manipulator is obtained to justify theoretical results. A shift mechanism is then implemented on the taurus shape, thus the motions of the robotic manipulator is further constrained. The difficulties in handling the motion constraints are discussed and an alternative approach is presented. The work presented in this dissertation uses both kinematic and dynamic based virtual manipulators as virtual simulators to address problems associated in both free and constrained motions. Implementation of both haptic display simulations in an experimental interaction system allows for the evaluation of the performance of the haptic interaction. Both implementations are general enough to allow researchers with any six degree-of-freedom robot to apply the approaches and continue in this area of research. The results are expected to improve on the current haptic display technology by a new type of optimal position controller and better algorithms to handle both holonomic and nonholonomic constraints.

Adaptive Impedance Control to Enhance Human Skill on a Haptic Interface System

Journal of Control Science and Engineering, 2012

Adaptive assistive control for a haptic interface system is proposed in the present paper. The assistive control system consists of three subsystems: a servo controller to match the response of the controlled machine to the virtual model, an online identifier of the operator’s control characteristics, and a variable dynamics control using adaptive mechanism. The adaptive mechanism tunes an impedance of the virtual model for the haptic device according to the identified operator’s characteristics so as to enhance the operator’s control performance. The adaptive law is derived by utilizing a Lyapunov candidate function. Using a haptic interface device composed by axy-stage, an effectiveness of the proposed control method was evaluated experimentally. As a result, it was confirmed that the operator’s characteristics can be estimated sufficiently and that performance of the operation was enhanced by the variable dynamics assistive control.