Leg Locomotion Adaption for Quadruped Robots with Ground Compliance Estimation

Locomotion control for quadruped robots is commonly applied on rigid terrains with modelled contact dynamics. However, the robot traversing different terrains is more important for real application. In this paper, a single-leg prototype and a test platform are built. The Cartesian coordinates of the foot-end are obtained through trajectory planning, and then, the virtual polar coordinates in the impedance control are obtained through geometric transformation. The deviation from the planned and actual virtual polar coordinates and the expected force recognized by the ground compliance identification system are sent to the impedance controller for different compliances. At last, several experiments are carried out for evaluating the performance including the ground compliance identification, the foot-end trajectory control, and the comparison between pure position control and impedance control.

Download Full-text

Stability-Guaranteed and High Terrain Adaptability Static Gait for Quadruped Robots

Sensors ◽

10.3390/s20174911 ◽

2020 ◽

Vol 20 (17) ◽

pp. 4911

Author(s):

Qian Hao ◽

Zhaoba Wang ◽

Junzheng Wang ◽

Guangrong Chen

Keyword(s):

Impedance Control ◽

Stability Margin ◽

Planning Method ◽

Legged Robots ◽

Gait Planning ◽

Quadruped Locomotion ◽

Quadruped Robots ◽

Adjustment Strategy ◽

Compliant Behavior ◽

The Stability

Stability is a prerequisite for legged robots to execute tasks and traverse rough terrains. To guarantee the stability of quadruped locomotion and improve the terrain adaptability of quadruped robots, a stability-guaranteed and high terrain adaptability static gait for quadruped robots is addressed. Firstly, three chosen stability-guaranteed static gaits: intermittent gait 1&2 and coordinated gait are investigated. In addition, then the static gait: intermittent gait 1, which is with the biggest stability margin, is chosen to do a further research about quadruped robots walking on rough terrains. Secondly, a position/force based impedance control is employed to achieve a compliant behavior of quadruped robots on rough terrains. Thirdly, an exploratory gait planning method on uneven terrains with touch sensing and an attitude-position adjustment strategy with terrain estimation are proposed to improve the terrain adaptability of quadruped robots. Finally, the proposed methods are validated by simulations.

Download Full-text

Flexible-Joint Humanoid Balancing Augmentation via Full-State Feedback Variable Impedance Control

Journal of Mechanisms and Robotics ◽

10.1115/1.4049648 ◽

2021 ◽

Vol 13 (2) ◽

Author(s):

Emmanouil Spyrakos-Papastavridis ◽

Jian S. Dai

Keyword(s):

State Feedback ◽

Position Control ◽

Impedance Control ◽

Humanoid Robots ◽

Flexible Joint ◽

Model Free ◽

Floating Base ◽

Full State ◽

Full State Feedback ◽

Series Elastic Actuators

Abstract This paper attempts to address the quandary of flexible-joint humanoid balancing performance augmentation, via the introduction of the Full-State Feedback Variable Impedance Control (FSFVIC), and Model-Free Compliant Floating-base VIC (MCFVIC) schemes. In comparison to rigid-joint humanoid robots, efficient balancing control of compliant bipeds, powered by Series Elastic Actuators (or harmonic drives), requires the design of more sophisticated controllers encapsulating both the motor and underactuated link dynamics. It has been demonstrated that Variable Impedance Control (VIC) can improve robotic interaction performance, albeit by introducing energy-injecting elements that may jeopardize closed-loop stability. To this end, the novel FSFVIC and MCFVIC schemes are proposed, which amalgamate both collocated and non-collocated feedback gains, with power-shaping signals that are capable of preserving the system's stability/passivity during VIC. The FSFVIC and MCFVIC stably modulate the system's collocated state gains to augment balancing performance, in addition to the non-collocated state gains that dictate the position control accuracy. Utilization of arbitrarily low-impedance gains is permitted by both the FSFVIC and MCFVIC schemes propounded herein. An array of experiments involving the COmpliant huMANoid reveals that significant balancing performance amelioration is achievable through online modulation of the full-state feedback gains (VIC), as compared to utilization of invariant impedance control.

Download Full-text

Impedance Control of Dual-Arm Systems Based on the Object with Senseless Force

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.765-767.1920 ◽

2013 ◽

Vol 765-767 ◽

pp. 1920-1923

Author(s):

Li Jiang ◽

Yang Zhou ◽

Bin Wang ◽

Chao Yu

Keyword(s):

Numerical Simulations ◽

Relative Position ◽

Position Control ◽

Impedance Control ◽

Force Sensors ◽

Operational Space ◽

Novel Approach ◽

Control Scheme ◽

Statics And Dynamics ◽

Dual Arm

A novel approach to impedance control based on the object is proposed to control dual-arm systems with senseless force. Considering the motion of the object, the statics and dynamics of the dual-arm systems are modeled. Extending the dynamics of dual-arm system and the impedance of object to the operational space, impedance control with senseless force is presented. Simulations on a dual-arm system are carried out to demonstrate the performance of the proposed control scheme. Comparing with position control, results of numerical simulations show that the proposed scheme realizes suitable compliant behaviors in terms of the object, and minimizes the error of the relative position between the manipulators even without force sensors.

Download Full-text

Patient-Centered Robot-Aided Passive Neurorehabilitation Exercise Based on Safety-Motion Decision-Making Mechanism

BioMed Research International ◽

10.1155/2017/4185939 ◽

2017 ◽

Vol 2017 ◽

pp. 1-11 ◽

Cited By ~ 8

Author(s):

Lizheng Pan ◽

Aiguo Song ◽

Suolin Duan ◽

Zhuqing Yu

Keyword(s):

Decision Making ◽

Control Strategy ◽

Position Control ◽

Impedance Control ◽

Control Strategies ◽

Movement Speed ◽

Stroke Patients ◽

Patient Centered ◽

Motion Speed ◽

Clinical Experiments

Safety is one of the crucial issues for robot-aided neurorehabilitation exercise. When it comes to the passive rehabilitation training for stroke patients, the existing control strategies are usually just based on position control to carry out the training, and the patient is out of the controller. However, to some extent, the patient should be taken as a “cooperator” of the training activity, and the movement speed and range of the training movement should be dynamically regulated according to the internal or external state of the subject, just as what the therapist does in clinical therapy. This research presents a novel motion control strategy for patient-centered robot-aided passive neurorehabilitation exercise from the point of the safety. The safety-motion decision-making mechanism is developed to online observe and assess the physical state of training impaired-limb and motion performances and regulate the training parameters (motion speed and training rage), ensuring the safety of the supplied rehabilitation exercise. Meanwhile, position-based impedance control is employed to realize the trajectory tracking motion with interactive compliance. Functional experiments and clinical experiments are investigated with a healthy adult and four recruited stroke patients, respectively. The two types of experimental results demonstrate that the suggested control strategy not only serves with safety-motion training but also presents rehabilitation efficacy.

Download Full-text

Analysis and Optimization of Interpolation Points for Quadruped Robots Joint Trajectory

Complexity ◽

10.1155/2020/3507679 ◽

2020 ◽

Vol 2020 ◽

pp. 1-17

Author(s):

Mingfang Chen ◽

Kaixiang Zhang ◽

Sen Wang ◽

Fei Liu ◽

Jinxin Liu ◽

...

Keyword(s):

Trajectory Planning ◽

Pso Algorithm ◽

Joint Space ◽

Quadruped Robots ◽

Original Curve ◽

Temporal Domain ◽

Trajectory Simulation ◽

Physical Prototype ◽

Joint Trajectory Planning ◽

Actual Trajectory

Trajectory planning is the foundation of locomotion control for quadruped robots. This paper proposes a bionic foot-end trajectory which can adapt to many kinds of terrains and gaits based on the idea of trajectory planning combining Cartesian space with joint space. Trajectory points are picked for inverse kinematics solution, and then quintic polynomials are used to plan joint space trajectories. In order to ensure that the foot-end trajectory generated by the joint trajectory planning is closer to the original Cartesian trajectory, the distributions of the interpolation point are analyzed from the spatial domain to temporal domain. An evaluation function was established to assess the closeness degree between the actual trajectory and the original curve. Subsequently, the particle swarm optimization (PSO) algorithm and genetic algorithm (GA) for the points selection are used to obtain a more precise trajectory. Simulation and physical prototype experiments were included to support the correctness and effectiveness of the algorithms and the conclusions.

Download Full-text

Adaptive Sliding Mode Impedance Control of Single-Link Flexible Manipulators interacting with the Environment at an Unknown Intermediate Point

Robotica ◽

10.1017/s026357471900167x ◽

2019 ◽

Vol 38 (9) ◽

pp. 1642-1664 ◽

Cited By ~ 1

Author(s):

Ali Fayazi ◽

Naser Pariz ◽

Ali Karimpour ◽

V. Feliu-Batlle ◽

S. Hassan HosseinNia

Keyword(s):

Position Control ◽

Sliding Mode ◽

Impedance Control ◽

Detection Algorithm ◽

Reference Trajectory ◽

Constrained Motion ◽

Intermediate Point ◽

Control Scheme ◽

Single Link ◽

Motion Mode

SUMMARYThis paper proposes an adaptive robust impedance control for a single-link flexible arm when it encounters an environment at an unknown intermediate point. First, the intermediate collision point is estimated using a collision detection algorithm. The controller, then, switches from free to constrained motion mode. In the unconstrained motion mode, the exerted force to environment is nearly zero. Thus, the reference trajectory is a prescribed desired trajectory in position control. In the constrained motion mode, the reference trajectory is determined by the desired target dynamic impedance. The simulation results demonstrate the efficiency of proposed control scheme.

Download Full-text

Multi-Robot Trajectory Planning and Position/Force Coordination Control in Complex Welding Tasks

Applied Sciences ◽

10.3390/app9050924 ◽

2019 ◽

Vol 9 (5) ◽

pp. 924 ◽

Cited By ~ 3

Author(s):

Yahui Gan ◽

Jinjun Duan ◽

Ming Chen ◽

Xianzhong Dai

Keyword(s):

Trajectory Planning ◽

Cooperative Control ◽

Impedance Control ◽

Welding Process ◽

Coordination Control ◽

Control Approach ◽

Force Coordination ◽

Force Tracking ◽

Robot Systems ◽

Multi Robot

In this paper, the trajectory planning and position/force coordination control of multi-robot systems during the welding process are discussed. Trajectory planning is the basis of the position/ force cooperative control, an object-oriented hierarchical planning control strategy is adopted firstly, which has the ability to solve the problem of complex coordinate transformation, welding process requirement and constraints, etc. Furthermore, a new symmetrical internal and external adaptive variable impedance control is proposed for position/force tracking of multi-robot cooperative manipulators. Based on this control approach, the multi-robot cooperative manipulator is able to track a dynamic desired force and compensate for the unknown trajectory deviations, which result from external disturbances and calibration errors. In the end, the developed control scheme is experimentally tested on a multi-robot setup which is composed of three ESTUN industrial manipulators by welding a pipe-contact-pipe object. The simulations and experimental results are strongly proved that the proposed approach can finish the welding task smoothly and achieve a good position/force tracking performance.

Download Full-text

A hybrid impedance control scheme for underwater welding robots with a passive foundation in the controller domain

SIMULATION ◽

10.1177/0037549717693687 ◽

2017 ◽

Vol 93 (7) ◽

pp. 619-630 ◽

Cited By ~ 3

Author(s):

Sunil Kumar ◽

Vikas Rastogi ◽

Pardeep Gupta

Keyword(s):

Minimum Distance ◽

Position Control ◽

Robot Manipulator ◽

Impedance Control ◽

Graph Model ◽

Proportional Integral Derivative ◽

End Effector ◽

Flexible Arm ◽

Control Scheme ◽

Effective Stability

A hybrid impedance control scheme for the force and position control of an end-effector is presented in this paper. The interaction of the end-effector is controlled using a passive foundation with compensation gain. For obtaining the steady state, a proportional–integral–derivative controller is tuned with an impedance controller. The hybrid impedance controller is implemented on a terrestrial (ground) single-arm robot manipulator. The modeling is done by creating a bond graph model and efficacy is substantiated through simulation results. Further, the hybrid impedance control scheme is applied on a two-link flexible arm underwater robot manipulator for welding applications. Underwater conditions, such as hydrodynamic forces, buoyancy forces, and other disturbances, are considered in the modeling. During interaction, the minimum distance from the virtual wall is maintained. A simulation study is carried out, which reveals some effective stability of the system.

Download Full-text

Smooth transition adaptive hybrid impedance control for connector assembly

Industrial Robot the international journal of robotics research and application ◽

10.1108/ir-11-2017-0193 ◽

2018 ◽

Vol 45 (2) ◽

pp. 287-299 ◽

Cited By ~ 1

Author(s):

Jun Wu ◽

Fenglei Ni ◽

Yuanfei Zhang ◽

Shaowei Fan ◽

Qi Zhang ◽

...

Keyword(s):

Position Control ◽

Impedance Control ◽

Estimation Error ◽

Adaptive Controller ◽

Smooth Transition ◽

Reference Trajectory ◽

Content Type ◽

Dynamic Uncertainty ◽

Force Tracking ◽

Potential Applications

Purpose This paper aims to present a smooth transition adaptive hybrid impedance control for compliant connector assembly. Design/methodology/approach The dynamics of the manipulator is firstly presented with linear property. The controller used in connector assembly is inspired by human operation habits in similar tasks. The hybrid impedance control is adopted to apply force in the assembly direction and provide compliance in rest directions. The reference trajectory is implemented with an adaptive controller. Event-based switching strategy is conducted for a smooth transition from unconstrained to constrained space. Findings The method can ensure both ideal compliance behaviour with dynamic uncertainty and a smooth transition from unconstrained to constrained space. Also, the method can ensure compliant connector assembly with a good tolerance to the target estimation error. Practical implications The method can be applied in the connector assembly by “pushing” operation. The controller devotes efforts on force tracking and smooth transition, having potential applications in contact tasks in delicate environment. Originality/value As far as the authors know, the paper is original in providing a uniform controller for improving force and position control performance in both unconstrained and constrained space with dynamic uncertainty. The proposed controller can ensure a smooth transition by only adjusting parameters.

Download Full-text