scholarly journals Using Repetitive Control with Force Feedback to Reduce Impedance of Exoskeletons for Gait Training

2021 ◽  
Author(s):  
Robert McGrath ◽  
Fabrizio Sergi
Keyword(s):  
Force Feedback ◽  
Gait Training ◽  
Random Signal ◽  
Human Robot Interaction ◽  
Important Quality ◽  
Signal Period ◽  
Mass Spring ◽  
Proportional Controller ◽  
Repetitive Controller ◽  
Parameter Error

Transparent interaction, or the reduction of human-robot interaction forces, is an important quality of gait training exoskeletons. In this paper, we investigate the feasibility of using a repetitive controller for reducing impedance of gait training exoskeletons using force feedback. We used a two-mass spring damper model system, and simulated the application of repetitive force controllers with the objective of reducing the end-point impedance of the distal mass. We designed and applied three repetitive controllers: a 1st order, a 2nd order designed for random signal period error, and a 2nd order designed for constant signal period error. We compared these three repetitive controllers subject to plant model parameter error, random signal period error, and constant signal period error. Numerical simulations under nominal conditions show that via repetitive force control, it is possible to reduce the endpoint impedance to the targeted magnitude and RMSE force below the limit achievable with force controllers while guaranteeing passivity. Furthermore, we established that the application of a 2nd order repetitive controller designed for random period error is highly robust to random period error - exceeding the performance of the passive proportional controller up to 30% error of nominal frequency. Furthermore, this 2nd order repetitive controller designed for random period error maintains a 100% convergence rate through 60% plant parameter error.

An improved multipurpose field robot for installing construction materials

Robotica ◽  
2010 ◽  
Vol 28 (7) ◽  
pp. 945-957 ◽  
Author(s):  
Seungyeol Lee ◽  
Seungnam Yu ◽  
Seokjong Yu ◽  
Changsoo Han
Keyword(s):  
Force Feedback ◽  
Construction Materials ◽  
Human Robot Interaction ◽  
Work Environments ◽  
National Defense ◽  
Construction Sites ◽  
Robot Interaction ◽  
Hazardous Environments ◽  
Remote Sites ◽  
Field Robot

SUMMARYRecently, there has been a lot of interest concerning remote-controlled robot manipulation in hazardous environments including construction sites, national defense areas, and disaster areas. However, there are problems involving the method of remote control in unstructured work environments such as construction sites. In a previous study, to address these problems, a multipurpose field robot (MFR) system was described. Though the case studies on construction, to which “MFR for installing construction materials” was applied, however, we found some factors to be improved. In this paper, we introduce a prototype of improved multipurpose field robot (IMFR) for construction work. This prototype robot helps a human operator easily install construction materials in remote sites through an upgraded additional module. This module consists of a force feedback joystick and a monitoring device. The human–robot interaction and bilateral communication for strategic control is also described. To evaluate the proposed IMFR, the installation of construction materials was simulated. We simulated the process of installing construction materials, in this case a glass panel. The IMFR was expected to do more accurate work, safely, at construction sites as well as at environmentally hazardous areas that are difficult for humans to approach.

scholarly journals Plug-in direct particle swarm repetitive controller with a reduced dimensionality of a fitness landscape – a multi-swarm approach

2015 ◽  
Vol 63 (4) ◽  
pp. 857-866 ◽  
Author(s):  
B. Ufnalski ◽  
L.M. Grzesiak
Keyword(s):  
Performance Index ◽  
Fitness Landscape ◽  
Reference Signal ◽  
Particle Swarm ◽  
Control Signal ◽  
Voltage Source ◽  
Reference Frequency ◽  
Particle Swarm Optimizer ◽  
Signal Period ◽  
Repetitive Controller

Abstract The paper describes a modification to the recently developed plug-in direct particle swarm repetitive controller (PDPSRC) for the sine-wave constant-amplitude constant-frequency (CACF) voltage-source inverter (VSI). The original PDPSRC algorithm assumes that the particle swarm optimizer (PSO) takes into account a performance index defined over the whole reference signal period. Each particle stores all the samples of the control signal, e.g. α = 200 samples for a controller working at 10 kHz and the reference frequency equal to 50 Hz. Therefore, the fitness landscape (i.e. the performance index) is -dimensional ( D), which makes optimization challenging. That solution can be categorized as the single-swarm one. It has been previously shown that the swarm controller does not suffer from long-term stability issues encountered in the classic iterative learning controllers (ILC). However, the convergence of the swarm has to be kept at a relatively low rate to enable successful exploitation in the D search space, which in turn results in slow responsiveness of the PDPSRC. Here a multi-swarm approach is proposed in which we divide a dynamic optimization problem (DOP) among less dimensional swarms. The reference signal period is segmented into shorter intervals and the control signal is optimized in each interval independently by separate swarms. The effectiveness of the proposed approach is illustrated with the help of numerical experiments on the CACF VSI with an output LC filter operating under nonlinear loads.

Soft-Touch Haptics Modeling of Dynamic Surfaces

2011 ◽  
pp. 1160-1182
Author(s):  
Hanqiu Sun ◽  
Hui Chen
Keyword(s):  
Virtual Environments ◽  
Virtual Worlds ◽  
Force Feedback ◽  
Subdivision Surfaces ◽  
Haptic Information ◽  
Sense Of Presence ◽  
Soft Objects ◽  
Freeform Deformation ◽  
Constraint Modeling ◽  
Mass Spring

Virtual Reality applications strive to simulate real or imaginary scenes with which users can interact and perceive the effects of their actions in real time. Adding haptic information such as vibration, tactile array, and force feedback enhances the sense of presence in virtual environments. Haptics interfaces present new challenges in the situation where it is crucial for the operators to touch, grasp and manipulate rigid/soft objects in the immersive virtual worlds. Soft-touch haptics modeling is the core component in feeling and manipulating dynamic objects within the virtual environments. For adding the haptic sensations with interactive soft objects, the authors first present multiple force-reflecting dynamics in Loop subdivision surfaces, and further the haptic freeform deformation of soft objects through mass-spring Bezier volume lattice. The haptic constraint modeling based on metaballs is experimented to intuitively control the interactive force distribution within the dynamically constructed constraint, making the soft-touch simulation of objects simple to manipulate with enhanced realism.

On interacting with physics-based models of graphical objects

Robotica ◽  
2004 ◽  
Vol 22 (2) ◽  
pp. 223-230 ◽  
Author(s):  
Shahram Payandeh ◽  
John Dill ◽  
Zhu Liang Cai
Keyword(s):  
Force Feedback ◽  
Time History ◽  
Local Deformation ◽  
Polygonal Mesh ◽  
Physical Environments ◽  
Trajectory Mapping ◽  
Realistic Representation ◽  
History Of ◽  
Reaction Forces ◽  
Mass Spring

Enhancing graphical objects whose behaviors are governed by the laws of physics is an important requirement in modeling virtual physical environments. In such environments, the user can interact with graphical objects and is able to either feel the simulated reaction forces through a physical computer interface such as a force feedback mouse or through such interactions, objects behave in a natural way. One of the key requirements for such interaction is determination of the type of contact between the user controlled object and the objects representing the environment. This paper presents an approach for reconstructing the contact configuration between two objects. This is accomplished through usage of the time history of the motion of the approaching objects for inverse trajectory mapping of polygonal representation. In the case of deformable objects and through usage of mass-spring-damper system this paper also presents a special global filter that can map the local deformation of an object to the adjacent vertices of polygonal mesh. In addition to offering a fast computational framework, the proposed method also offers more realistic representation of the deformation. The results of this paper are shown through detailed examples and comparison analysis using different computational platforms.

scholarly journals Analysis and Design of A PMQR-Type Repetitive Control Scheme for Grid-Connected H6 Inverters

2019 ◽  
Vol 9 (6) ◽  
pp. 1198
Author(s):  
Xiaohui Yang ◽  
Peiyun Liu ◽  
Shaoping Xu ◽  
Shichao Liu
Keyword(s):  
Single Phase ◽  
Control Strategies ◽  
Repetitive Control ◽  
Analysis And Design ◽  
Computational Costs ◽  
Comparison Results ◽  
Control Scheme ◽  
Lc Filter ◽  
Proportional Controller ◽  
Repetitive Controller

There exist several challenges in the implementation of proportional multiple quasi-resonant (PMQR) control strategies in single-phase grid-connected H6 inverters, such as high computational costs and design complexity. To overcome these challenges, this paper proposes a proportional multiple quasi-resonant (PMQR)-type repetitive control (PMQR-type RC) scheme for single-phase grid-connected H6 inverters. In the control scheme, a repetitive controller and a proportional controller run in parallel. The repetitive controller is to improve the steady-state harmonics compensation ability, while the proportional controller can enhance the transient performance of the system. Both theoretical stability analysis and detailed design steps regarding the proposed control scheme are introduced. Finally, comparison results on a typical single-phase grid-connected H6 inverter with LC filter under a variety of control methods verify the capability of suppressing harmonics and the robust performance of the proposed control strategy against grid disturbances.

Mechanical Design and Evaluation of a Novel Knee-Ankle-Foot Robot for Rehabilitation

2015 ◽  
Author(s):  
Gong Chen ◽  
Zhao Guo ◽  
Haoyong Yu
Keyword(s):  
Mechanical Design ◽  
Gait Training ◽  
Human Robot Interaction ◽  
Robot Interaction ◽  
Gait Patterns ◽  
Gait Biomechanics ◽  
Leg Muscles ◽  
In Series ◽  
Translational Spring ◽  
Selection Of

This paper presents the mechanical design and evaluation of a knee-ankle-foot robot, which is compact, modular, and portable for stroke patients to carry out overground gait training at outpatient and home settings. The robot is driven by a novel series elastic actuator (SEA) for safe human-robot interaction. The SEA employs one soft translational spring in series with a stiff torsion spring to achieve high intrinsic compliance and the capacity of providing peak force. The robotic joint mechanism and the selection of the actuator springs are optimized based on gait biomechanics to achieve portability and capability. The robot demonstrated stable and accuracy force control in experiments conducted on healthy subjects with overground walking. Major leg muscles of the subjects showed reduced level of activations (Electromyography, EMG) while maintaining normal gait patterns with robotic assistances, indicating the robot’s capability of providing effective gait assistance.

scholarly journals Wearable Biofeedback Improves Human-Robot Compliance during Ankle-Foot Exoskeleton-Assisted Gait Training: A Pre-Post Controlled Study in Healthy Participants

Sensors ◽  
2020 ◽  
Vol 20 (20) ◽  
pp. 5876
Author(s):  
Cristiana Pinheiro ◽  
Joana Figueiredo ◽  
Nuno Magalhães ◽  
Cristina P. Santos
Keyword(s):  
Group Performance ◽  
Gait Training ◽  
User Participation ◽  
Human Robot Interaction ◽  
Controlled Study ◽  
P Value ◽  
Joint Motion ◽  
Robot Interaction ◽  
Post Stroke ◽  
Healthy Participants

The adjunctive use of biofeedback systems with exoskeletons may accelerate post-stroke gait rehabilitation. Wearable patient-oriented human-robot interaction-based biofeedback is proposed to improve patient-exoskeleton compliance regarding the interaction torque’s direction (joint motion strategy) and magnitude (user participation strategy) through auditory and vibrotactile cues during assisted gait training, respectively. Parallel physiotherapist-oriented strategies are also proposed such that physiotherapists can follow in real-time a patient’s motor performance towards effective involvement during training. A preliminary pre-post controlled study was conducted with eight healthy participants to conclude about the biofeedback’s efficacy during gait training driven by an ankle-foot exoskeleton and guided by a technical person. For the study group, performance related to the interaction torque’s direction increased during (p-value = 0.07) and after (p-value = 0.07) joint motion training. Further, the performance regarding the interaction torque’s magnitude significantly increased during (p-value = 0.03) and after (p-value = 68.59 × 10−3) user participation training. The experimental group and a technical person reported promising usability of the biofeedback and highlighted the importance of the timely cues from physiotherapist-oriented strategies. Less significant improvements in patient–exoskeleton compliance were observed in the control group. The overall findings suggest that the proposed biofeedback was able to improve the participant-exoskeleton compliance by enhancing human-robot interaction; thus, it may be a powerful tool to accelerate post-stroke ankle-foot deformity recovery.

Soft-Touch Haptics Modeling of Dynamic Surfaces

2011 ◽  
pp. 14-35
Author(s):  
Hanqiu Sun ◽  
Hui Chen
Keyword(s):  
Virtual Environments ◽  
Virtual Worlds ◽  
Force Feedback ◽  
Subdivision Surfaces ◽  
Haptic Information ◽  
Sense Of Presence ◽  
Soft Objects ◽  
Freeform Deformation ◽  
Constraint Modeling ◽  
Mass Spring

Virtual Reality applications strive to simulate real or imaginary scenes with which users can interact and perceive the effects of their actions in real time. Adding haptic information such as vibration, tactile array, and force feedback enhances the sense of presence in virtual environments. Haptics interfaces present new challenges in the situation where it is crucial for the operators to touch, grasp and manipulate rigid/soft objects in the immersive virtual worlds. Soft-touch haptics modeling is the core component in feeling and manipulating dynamic objects within the virtual environments. For adding the haptic sensations with interactive soft objects, the authors first present multiple force-reflecting dynamics in Loop subdivision surfaces, and further the haptic freeform deformation of soft objects through mass-spring Bezier volume lattice. The haptic constraint modeling based on metaballs is experimented to intuitively control the interactive force distribution within the dynamically constructed constraint, making the soft-touch simulation of objects simple to manipulate with enhanced realism.

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