A New Indirect Actuation Principle for Safe Physical Human-Robot Interactions

2013 ◽  
Author(s):  
Laure Esteveny ◽  
Laurent Barbé ◽  
Bernard Bayle
Keyword(s):  
Control Strategy ◽  
Closed Loop ◽  
Position Control ◽  
Design Procedure ◽  
Degree Of Freedom ◽  
Safety Concerns ◽  
Gravity Forces ◽  
Innovative Solution ◽  
Trajectory Following ◽  
Proportional Derivative Controller

Intrinsically safe mechanisms represent an innovative solution to develop physical human-robot interactions. These systems are characterized by low masses, inertia and torques. In this paper, an innovative actuation strategy is presented, focused on safety concerns. The system is first statically balanced to compensate gravity forces in any configuration. Our contribution then lies in the design of a mechanism that modifies the system balancing, making it possible to follow a planned trajectory or to remain in contact with a moving environment, without developing large forces. This principle is illustrated with an elementary one degree of freedom arm. The whole design procedure is described, so as to define properly the arm parameters for a given task. A closed loop position control strategy is then proposed in order to drive the mechanism. It uses a proportional-derivative controller with configuration dependent gains, whose efficiency is illustrated by trajectory following and interaction simulations.

Sensitivity Reduction of Constraint Forces and Position Control for Mechanical Descriptor Systems

1997 ◽  
Vol 119 (2) ◽  
pp. 286-289
Author(s):  
Dan-chi Jiang ◽  
Wei-Yong Yan ◽  
K. L. Teo
Keyword(s):  
State Feedback ◽  
Closed Loop ◽  
Position Control ◽  
Design Procedure ◽  
Descriptor Systems ◽  
Algebraic Riccati Equation ◽  
Systematic Design ◽  
Closed Loop System ◽  
Constraint Forces ◽  
Constrained System

This paper deals with the position and force control for mechanical systems with holonomic constraints. Our concern is the design of a feedback controller such that the closed-loop system has a satisfactory transient response and is less sensitive to various types of disturbances. Using an appropriate transformation, the constrained system is converted into an unconstrained system of lower order. Then, an H∞, control problem involving the reduced system is formulated. In the case of state feedback, a systematic design procedure for solving the problem is presented, where the key step is the solution of an algebraic Riccati equation. An example is given to illustrate the effectiveness of the proposed method.

scholarly journals Dynamic External Force Feedback Loop Control of a Robot Manipulator Using a Neural Compensator—Application to the Trajectory Following in an Unknown Environment

2009 ◽  
Vol 19 (1) ◽  
pp. 113-126 ◽  
Author(s):  
Farid Ferguene ◽  
Redouane Toumi
Keyword(s):  
External Force ◽  
Control Strategy ◽  
Feedback Loop ◽  
Force Feedback ◽  
Position Control ◽  
Robot Manipulator ◽  
Suggested Approach ◽  
Loop Control ◽  
Unknown Environment ◽  
Trajectory Following

Dynamic External Force Feedback Loop Control of a Robot Manipulator Using a Neural Compensator—Application to the Trajectory Following in an Unknown EnvironmentForce/position control strategies provide an effective framework to deal with tasks involving interaction with the environment. One of these strategies proposed in the literature is external force feedback loop control. It fully employs the available sensor measurements by operating the control action in a full dimensional space without using selection matrices. The performance of this control strategy is affected by uncertainties in both the robot dynamic model and environment stiffness. The purpose of this paper is to improve controller robustness by applying a neural network technique in order to compensate the effect of uncertainties in the robot model. We show that this control strategy is robust with respect to payload uncertainties, position and environment stiffness, and dry and viscous friction. Simulation results for a three degrees-of-freedom manipulator and various types of environments and trajectories show the effectiveness of the suggested approach compared with classical external force feedback loop structures.

scholarly journals Control Strategy for Direct Teaching of Non-Mechanical Remote Center Motion of Surgical Assistant Robot with Force/Torque Sensor

2021 ◽  
Vol 11 (9) ◽  
pp. 4279
Author(s):  
Minhyo Kim ◽  
Youqiang Zhang ◽  
Sangrok Jin
Keyword(s):  
Control Strategy ◽  
Position Control ◽  
Dimensional Space ◽  
Degree Of Freedom ◽  
Torque Sensor ◽  
Motion Generation ◽  
End Effector ◽  
Generation Algorithm ◽  
Direct Teaching ◽  
Collaborative Robot

This paper presents a control strategy that secures both precision and manipulation sensitivity of remote center motion with direct teaching for a surgical assistant robot. Remote center motion is an essential function of conventional laparoscopic surgery, and the most intuitive way a surgeon manipulates a robot is through direct teaching. The surgical assistant robot must maintain the position of the insertion port in three-dimensional space during the four-degree-of-freedom motions such as pan, tilt, spin, and forward/backward. In addition, the robot should move smoothly when controlling it with the hands during the surgery. In this study, a six-degree-of-freedom collaborative robot performs the cone-shaped trajectory with pan and tilt motion of an end-effector keeping the position of the remote center. Instead of the bulky mechanically constrained remote center motion mechanism, a conventional collaborative robot is used to mimic the wrist movement of a scrub nurse. A force/torque sensor that is attached between the robot and end-effector estimates the surgeon’s intention. A direct teaching control strategy based on position control is applied to guarantee precise remote center position maintenance performance. A motion generation algorithm is designed to generate motion by utilizing a force/torque sensor value. The parameters of the motion generation algorithm are optimized so that the robot can be operated with uniform sensitivity in all directions. The precision of remote center motion and the torque required for direct teaching are analyzed through pan and tilt motion experiments.

Two Degree-of-Freedom Hysteresis Compensation for a Dynamic Mirror With Antagonistic Piezoelectric Stack Actuation

2013 ◽  
Author(s):  
James A. Mynderse ◽  
George T. C. Chiu
Keyword(s):  
Input Signal ◽  
Control Strategy ◽  
Closed Loop ◽  
Loop System ◽  
Degree Of Freedom ◽  
Closed Loop System ◽  
Loop Control ◽  
Hysteresis Compensation ◽  
Hysteresis Control ◽  
Two Degree Of Freedom

A methodology for designing a low-computation, high-bandwidth strategy for closed-loop control of a hysteretic system without a priori knowledge of the desired trajectory is presented. The resulting two degree-of-freedom hysteresis control strategy is applied to a dynamic mirror with antagonistic piezoelectric stack actuation. Hysteresis compensator is performed by a finite state machine switching polynomials for hysteresis inversion based on the input signal slope. Residual error after hysteresis compensation is corrected by an LQR feedback controller. Experimental results demonstrate effectiveness of the hysteresis compensator and closed-loop system under the proposed hysteresis control strategy. For the triangular input signal tested, the closed-loop system achieves a 91.5% reduction in hysteresis uncertainty with 60 kHz sample rate.

scholarly journals Fault-tolerant control strategy for actuator faults using LPV techniques: Application to a two degree of freedom helicopter

2012 ◽  
Vol 22 (1) ◽  
pp. 161-171 ◽  
Author(s):  
Saúl de Oca ◽  
Vicenç Puig ◽  
Marcin Witczak ◽  
Łukasz Dziekan
Keyword(s):  
Control Strategy ◽  
Fault Tolerant ◽  
Design Procedure ◽  
Fault Tolerant Control ◽  
Degree Of Freedom ◽  
Fault Identification ◽  
Linear Matrix ◽  
Actuator Faults ◽  
Control Schemes ◽  
Two Degree Of Freedom

Fault-tolerant control strategy for actuator faults using LPV techniques: Application to a two degree of freedom helicopter In this paper, a Fault Tolerant Control (FTC) strategy for Linear Parameter Varying (LPV) systems that can be used in the case of actuator faults is proposed. The idea of this FTC method is to adapt the faulty plant instead of adapting the controller to the faulty plant. This approach can be seen as a kind of virtual actuator. An integrated FTC design procedure for the fault identification and fault-tolerant control schemes using LPV techniques is provided as well. Fault identification is based on the use of an Unknown Input Observer (UIO). The FTC controller is implemented as a state feedback controller and designed using polytopic LPV techniques and Linear Matrix Inequality (LMI) regions in such a way as to guarantee the closed-loop behavior in terms of several LMI constraints. To assess the performance of the proposed approach, a two degree of freedom helicopter is used.

Stiffness and Compliance Control in Dynamical Systems Driven by Muscle-Like Actuators

2009 ◽  
Author(s):  
Federico Lorussi ◽  
Claudia Caudai ◽  
Danilo De Rossi ◽  
Stefano Galatolo
Keyword(s):  
Control Strategy ◽  
Closed Loop ◽  
Position Control ◽  
Kinematic Chain ◽  
Point Of View ◽  
Compliance Control ◽  
Loop Control ◽  
Kinematic Chains ◽  
Bounded Perturbation ◽  
Fixed Quantity

This work reports on the design and the feed forward stiffness control of bioinspired kinematic chains from a static and a dynamic point of view. While position control is clearly referred to common geometrical lagrangian coordinates for the considered system, in order to deal with the stiffness or compliance of the chain, especially in dynamic cases, global and less intuitive variables have to be defined and used. The advantage deriving from a similar control strategy can be important when the chain is part of a complex dynamic system or the computational resources are scarce. By defining and controlling stiffness or compliance for a certain position or trajectory, we can state that, even if the system is not continuously monitored in closed loop, a bounded perturbation cannot produce equilibrium point or trajectory variations greater than a fixed quantity. In a closed loop control strategy, the described methodology can be implemented during the time between two consecutive output sampling and feedback inputs. On the other hand, compliance control permits a kinematic chain to interact with objects without causing damages even if errors in position occur. In this work, the compliance and stiffness concepts, inspired to common reasoning in biological motor control theory, are generalized to a dynamic case and endowed with a mathematical architecture.

An LPV Approach to Obstacle-Sensitive Trajectory Regulation

2009 ◽  
Author(s):  
Mazen Farhood ◽  
Eric Feron
Keyword(s):  
Control Strategy ◽  
Design Parameter ◽  
Closed Loop ◽  
Degree Of Freedom ◽  
And Performance ◽  
Three Degree Of Freedom ◽  
Parameter Dependent ◽  
Strategy Changes ◽  
Loop Stability

The paper focuses on the control of vehicular systems along trajectories in the presence of obstacles. We design parameter-dependent controllers which guarantee closed-loop stability and performance of the vehicle’s regulation loop. In addition, the control strategy changes depending on the position of the vehicle in the obstacle environment so that the critical outputs are given the most attention. We also provide a fast and easy-to-implement algorithm for online controller construction. Last, the proposed approach is applied to a three-degree-of-freedom helicopter.

scholarly journals A Closed-Loop Strategy of Active Differential Clutch Control

2009 ◽  
Author(s):  
Vladimir Ivanovic´ ◽  
Josˇko Deur ◽  
Matthew Hancock ◽  
Francis Assadian
Keyword(s):  
Control Strategy ◽  
Closed Loop ◽  
Position Control ◽  
Free Play ◽  
Applied Force ◽  
Experimental Setup ◽  
Wet Clutch ◽  
Strategy Performance ◽  
Analysis Of Dynamics ◽  
Clutch Control

The paper presents experimentally supported control-oriented analysis of dynamics of an active differential wet clutch actuated by a geared DC motor. A closed-loop clutch control strategy is proposed. The strategy is based on experimentally obtained hysteresis-free clutch applied force vs. motor position curve and related closed-loop motor position control. A controller algorithm is proposed to compensate for the effect of clutch free-play variations due to clutch wear. The proposed control strategy performance is verified on a wet clutch experimental setup.

Robust Two-degree-of-freedom Control Based on H∞ Method for PMSM Drive System

2020 ◽  
Vol 13 (4) ◽  
pp. 496-506
Author(s):  
Qixin Zhu ◽  
Lei Xiong ◽  
Hongli Liu ◽  
Yonghong Zhu ◽  
Guoping Zhang
Keyword(s):  
Control System ◽  
Control Theory ◽  
Position Control ◽  
Dynamic Performance ◽  
Servo System ◽  
Degree Of Freedom ◽  
Trade Off ◽  
Standard Design ◽  
Position Controller ◽  
Two Degree Of Freedom

Background: The conventional method using one-degree-of-freedom (1DOF) controller for Permanent Magnet Synchronous Motor (PMSM) servo system has the trade-off problem between the dynamic performance and the robustness. Methods: In this paper, by using H∞ control theory, a novel robust two-degree-of-freedom (2DOF) controller has been proposed to improve the position control performance of PMSM servo system. Using robust control theory and 2DOF control theory, a H∞ robust position controller has been designed and discussed in detail. Results: The trade-off problem between the dynamic performance and robustness which exists in one-degree-of-freedom (1DOF) control can be dealt with by the application of 2DOF control theory. Then, through H∞ control theory, the design of robust position controller can be translated to H∞ robust standard design problem. Moreover, the control system with robust controller has been proved to be stable. Conclusion: Further simulation results demonstrate that compared with the conventional PID control, the designed control system has better robustness and attenuation to the disturbance of load impact.

Iterative feedback control based on frequency response model for a six-degree-of-freedom micro-vibration platform

2021 ◽  
pp. 107754632199731
Author(s):  
He Zhu ◽  
Shuai He ◽  
Zhenbang Xu ◽  
XiaoMing Wang ◽  
Chao Qin ◽  
...  
Keyword(s):  
Feedback Control ◽  
Frequency Response ◽  
Control Strategy ◽  
Degree Of Freedom ◽  
Small Displacement ◽  
Response Model ◽  
Parameter Uncertainties ◽  
Micro Vibration ◽  
Six Degree Of Freedom ◽  
Iterative Feedback

In this article, a six-degree-of-freedom (6-DOF) micro-vibration platform (6-MVP) based on the Gough–Stewart configuration is designed to reproduce the 6-DOF micro-vibration that occurs at the installation surfaces of sensitive space-based instruments such as large space optical loads and laser communications equipment. The platform’s dynamic model is simplified because of the small displacement characteristics of micro-vibrations. By considering the multifrequency line spectrum characteristics of micro-vibrations and the parameter uncertainties, an iterative feedback control strategy based on a frequency response model is designed, and the effectiveness of the proposed control strategy is verified by performing integrated simulations. Finally, micro-vibration experiments are performed with a 10 kg load on the platform. The results of these micro-vibration experiments show that after several iterations, the amplitude control errors are less than 3% and the phase control errors are less than 1°. The control strategy presented in this article offers the advantages of a simple algorithm and high precision and it can also be used to control other similar micro-vibration platforms.

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