scholarly journals Position Control for Soft Actuators, Next Steps toward Inherently Safe Interaction

Electronics ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 1116
Author(s):  
Dongshuo Li ◽  
Vaishnavi Dornadula ◽  
Kengyu Lin ◽  
Michael Wehner
Keyword(s):  
Visual Servoing ◽  
Position Control ◽  
Low Cost ◽  
Deformation Characteristic ◽  
Human Robot Interaction ◽  
Human Interaction ◽  
Soft Robots ◽  
Great Opportunity ◽  
Control Approach ◽  
Soft Actuators

Soft robots present an avenue toward unprecedented societal acceptance, utility in populated environments, and direct interaction with humans. However, the compliance that makes them attractive also makes soft robots difficult to control. We present two low-cost approaches to control the motion of soft actuators in applications common in human-interaction tasks. First, we present a passive impedance approach, which employs restriction to pneumatic channels to regulate the inflation/deflation rate of a pneumatic actuator and eliminate the overshoot/oscillation seen in many underdamped silicone-based soft actuators. Second, we present a visual servoing feedback control approach. We present an elastomeric pneumatic finger as an example system on which both methods are evaluated and compared to an uncontrolled underdamped actuator. We perturb the actuator and demonstrate its ability to increase distal curvature around the obstacle and maintain the desired end position. In this approach, we use the continuum deformation characteristic of soft actuators as an advantage for control rather than a problem to be minimized. With their low cost and complexity, these techniques present great opportunity for soft robots to improve human–robot interaction.

Stiffness Control of Parallel Continuum Robots

2018 ◽  
Author(s):  
Vincent Aloi ◽  
Caroline Black ◽  
Caleb Rucker
Keyword(s):  
Position Control ◽  
Target Position ◽  
Human Robot Interaction ◽  
Force Measurements ◽  
Modeling Framework ◽  
Continuum Robots ◽  
Integral Control ◽  
Control Approach ◽  
Cosserat Rods ◽  
Stiffness Control

Parallel continuum robots can provide compact, compliant manipulation of tools in robotic surgery and larger-scale human robot interaction. In this paper we address stiffness control of parallel continuum robots using a general nonlinear kinetostatic modeling framework based on Cosserat rods. We use a model formulation that estimates the applied end-effector force and pose using actuator force measurements. An integral control approach then modifies the commanded target position based on the desired stiffness behavior and the estimated force and position. We then use low-level position control of the actuators to achieve the modified target position. Experimental results show that after calibration of a single model parameter, the proposed approach achieves accurate stiffness control in various directions and poses.

Enabling impedance-based physical human–multi–robot collaboration: Experiments with four torque-controlled manipulators

2021 ◽  
pp. 027836492110536
Author(s):  
Niels Dehio ◽  
Joshua Smith ◽  
Dennis L. Wigand ◽  
Pouya Mohammadi ◽  
Michael Mistry ◽  
...  
Keyword(s):  
Human Robot Interaction ◽  
Contact Forces ◽  
Torque Control ◽  
Human Interaction ◽  
Physical Interaction ◽  
Complex Situation ◽  
Control Approach ◽  
Model Based ◽  
Compliant Control ◽  
Multi Robot

Robotics research into multi-robot systems so far has concentrated on implementing intelligent swarm behavior and contact-less human interaction. Studies of haptic or physical human-robot interaction, by contrast, have primarily focused on the assistance offered by a single robot. Consequently, our understanding of the physical interaction and the implicit communication through contact forces between a human and a team of multiple collaborative robots is limited. We here introduce the term Physical Human Multi-Robot Collaboration (PHMRC) to describe this more complex situation, which we consider highly relevant in future service robotics. The scenario discussed in this article covers multiple manipulators in close proximity and coupled through physical contacts. We represent this set of robots as fingers of an up-scaled agile robot hand. This perspective enables us to employ model-based grasping theory to deal with multi-contact situations. Our torque-control approach integrates dexterous multi-manipulator grasping skills, optimization of contact forces, compensation of object dynamics, and advanced impedance regulation into a coherent compliant control scheme. For this to achieve, we contribute fundamental theoretical improvements. Finally, experiments with up to four collaborative KUKA LWR IV+ manipulators performed both in simulation and real world validate the model-based control approach. As a side effect, we notice that our multi-manipulator control framework applies identically to multi-legged systems, and we execute it also on the quadruped ANYmal subject to non-coplanar contacts and human interaction.

scholarly journals Modelling and Control of a 2-DOF Robot Arm with Elastic Joints for Safe Human-Robot Interaction

2021 ◽  
Vol 8 ◽  
Author(s):  
Hua Minh Tuan ◽  
Filippo Sanfilippo ◽  
Nguyen Vinh Hao
Keyword(s):  
Control Algorithm ◽  
Position Control ◽  
Low Cost ◽  
Dynamic Environment ◽  
Human Robot Interaction ◽  
Robot Arm ◽  
Control Loop ◽  
Robot Interaction ◽  
Elastic Joint ◽  
Elastic Joints

Collaborative robots (or cobots) are robots that can safely work together or interact with humans in a common space. They gradually become noticeable nowadays. Compliant actuators are very relevant for the design of cobots. This type of actuation scheme mitigates the damage caused by unexpected collision. Therefore, elastic joints are considered to outperform rigid joints when operating in a dynamic environment. However, most of the available elastic robots are relatively costly or difficult to construct. To give researchers a solution that is inexpensive, easily customisable, and fast to fabricate, a newly-designed low-cost, and open-source design of an elastic joint is presented in this work. Based on the newly design elastic joint, a highly-compliant multi-purpose 2-DOF robot arm for safe human-robot interaction is also introduced. The mechanical design of the robot and a position control algorithm are presented. The mechanical prototype is 3D-printed. The control algorithm is a two loops control scheme. In particular, the inner control loop is designed as a model reference adaptive controller (MRAC) to deal with uncertainties in the system parameters, while the outer control loop utilises a fuzzy proportional-integral controller to reduce the effect of external disturbances on the load. The control algorithm is first validated in simulation. Then the effectiveness of the controller is also proven by experiments on the mechanical prototype.

Vision-based control of an underactuated flying robot with input delay

2016 ◽  
Vol 40 (2) ◽  
pp. 446-455 ◽  
Author(s):  
Hamed Jabbari Asl ◽  
Seyyed H Mahdioun ◽  
Jungwon Yoon
Keyword(s):  
Visual Servoing ◽  
Position Control ◽  
Image Plane ◽  
Dynamic Surface Control ◽  
Image Features ◽  
Dynamic Surface ◽  
Complete Control ◽  
Control Approach ◽  
Angular Velocities ◽  
Systems Simulation

In this paper a vision-based tracking controller is designed for the quadrotor vertical take-off and landing of an unmanned aerial vehicle. An imaged-based visual servoing approach is utilised to localise the quadrotor with respect to a moving target. Perspective image moments are used to define the visual features, which are projected on a rotated image plane to simplify the image dynamics. Attitude information and angular velocities are assumed to be available and the controller uses the flow of image features as the linear velocity cue. Presence of delay in processing and communication is modelled as a constant time delay in the force input of the translational dynamics, where a controller is designed for theses dynamics to compensate the delay effect. This controller is saturated in order to meet the quadrotor model constraint. A dynamic surface control approach is utilised for the rotational dynamics to track the desired attitude, defined through the position control loop. The stability properties of the complete control scheme are analysed using a theory of nonlinear cascaded systems. Simulation examples are provided in both nominal and perturbed conditions which show the effectiveness of the proposed theoretical results.

scholarly journals A Dual-origami  Design Enables the Quasi-sequential Deployment and Bending  Motion of Soft Robots and Grippers

2021 ◽  
Author(s):  
Woongbae Kim ◽  
Jaemin Eom ◽  
Kyujin Cho
Keyword(s):  
Fused Deposition Modeling ◽  
Low Cost ◽  
Robotic Systems ◽  
Soft Robots ◽  
Fused Deposition ◽  
Sealing Performance ◽  
Fluidic Actuators ◽  
Deposition Modeling ◽  
Soft Actuators ◽  
Design Guidance

Soft fluidic actuators produce continuous and life-like motions that are intrinsically safe, but current designs are not yet mature enough to enable large deployment with high force and low-cost fabrication methods. Here, soft fluidic actuators with two superimposed origami architectures are reported. Driven by a fluid input, the presented dual-origami soft actuators produce quasi-sequential deployment and bending motion that is guided by unsymmetric unfolding of low-stretchable origami components. The dominance between the deployment and bending can be shifted by varying the unfolding behavior, enabling pre-programming of the motion. The proposed origami-inspired soft actuators are directly fabricated by low-cost fused deposition modeling 3D-printing, and subjected to a heat treatment post-processing to enhance the fluid sealing performance. Finally, soft gripper applications are presented and they successfully demonstrate gripping tasks that each requires strength, delicacy, precision and dexterity. The dual-origami approach offers a design guidance for soft robots to embody grow-and-retract motion with a small initial form factor, promising for applications in next-generation soft robotic systems.

scholarly journals A Dual-origami  Design Enables the Quasi-sequential Deployment and Bending  Motion of Soft Robots and Grippers

2021 ◽  
Author(s):  
Woongbae Kim ◽  
Jaemin Eom ◽  
Kyujin Cho
Keyword(s):  
Fused Deposition Modeling ◽  
Low Cost ◽  
Robotic Systems ◽  
Soft Robots ◽  
Fused Deposition ◽  
Sealing Performance ◽  
Fluidic Actuators ◽  
Deposition Modeling ◽  
Soft Actuators ◽  
Design Guidance

Soft fluidic actuators produce continuous and life-like motions that are intrinsically safe, but current designs are not yet mature enough to enable large deployment with high force and low-cost fabrication methods. Here, soft fluidic actuators with two superimposed origami architectures are reported. Driven by a fluid input, the presented dual-origami soft actuators produce quasi-sequential deployment and bending motion that is guided by unsymmetric unfolding of low-stretchable origami components. The dominance between the deployment and bending can be shifted by varying the unfolding behavior, enabling pre-programming of the motion. The proposed origami-inspired soft actuators are directly fabricated by low-cost fused deposition modeling 3D-printing, and subjected to a heat treatment post-processing to enhance the fluid sealing performance. Finally, soft gripper applications are presented and they successfully demonstrate gripping tasks that each requires strength, delicacy, precision and dexterity. The dual-origami approach offers a design guidance for soft robots to embody grow-and-retract motion with a small initial form factor, promising for applications in next-generation soft robotic systems.

scholarly journals Self-Sensing Pneumatic Compressing Actuator

2020 ◽  
Vol 14 ◽  
Author(s):  
Nan Lin ◽  
Hui Zheng ◽  
Yuxuan Li ◽  
Ruolin Wang ◽  
Xiaoping Chen ◽  
...  
Keyword(s):  
Load Capacity ◽  
Low Cost ◽  
Axial Direction ◽  
Force Sensor ◽  
Human Robot Interaction ◽  
High Price ◽  
Flexible Membrane ◽  
Potential Safety ◽  
Output Force ◽  
Soft Actuators

Using soft pneumatic actuator is a feasible solution in the complex unstructured environment, owing to their inherent compliance, light weight, and safety. However, due to the limitations of soft actuators' materials and structures, they fall short of motion accuracy and load capacity, or need large-size, bulky compressors. Meanwhile, in order to gain better control, it is essential for them to sense the environments as well. This leads to high-price sensors or a complicated manufacture technique. Here, a self-sensing vacuum soft actuation structure is proposed, aiming at acquiring good balance among precision, output force, and actuation pressure. The actuator mainly comprises a flexible membrane and a compression spring. When actuated, the flexible membrane outside the actuator compresses the internal spring skeleton, realizing large contractile motion in axial direction. Its built-in force sensor can indirectly measure the absolute displacement of the actuator with certain accuracy (about 5% F.S.). Besides, it does not require high actuation pressure to generate enough output force. The actuator is quite easy to manufacture with low cost, and there are a variety of materials to choose from. We established quasi-static models for actuators built of two different kinds of membrane materials, and tested their accuracy and output force. In addition, to break through the limits of vacuum actuation, a method of positive-negative pressure combined actuation has been proposed, which lowers the requirements for air source equipments, increases actuation pressure, and reduces potential safety threats at the same time. This kind of soft actuators can also effectively resist and detect impacts. The design of a two-finger dexterous robot hand and robot joint based on this soft actuator illustrates its broad application prospects in the fields of mobile robots, wearable devices, and human–robot interaction.

Modeling and Control of a Hybrid Wheeled Legged Robot: Disturbance Analysis

2020 ◽  
Author(s):  
Fahad Raza ◽  
Dai Owaki ◽  
Mitsuhiro Hayashibe
Keyword(s):  
Position Control ◽  
Control Method ◽  
System Modeling ◽  
Linear Quadratic Regulator ◽  
Human Robot Interaction ◽  
Physical Disorder ◽  
Legged Robot ◽  
Linear Quadratic ◽  
Control Approach ◽  
Lqr Control

Abstract The most common cause of injuries among older adults is falling. Recently, there have been numerous developments in assistive and exoskeleton systems. However, comparatively little work is being done on systems that may help people to keep an upright position and avoid falling over. In this preliminary work, we investigate the feasibility of the wheel-legged robot as a balance-assist system for the people who cannot maintain balance and walk because of an injury, old age, or neurological or physical disorder. We perform motion stability analyses of the wheel-legged robot under different conditions such as system modeling errors, sensor noise, and external disturbances. The linear quadratic regulator (LQR) control approach is adopted for balancing, steering, and translational position control of the robot. To validate our control framework and visualize results, the robot is modeled and tested in the Gazebo simulator using ROS (Robot Operating System). Subsequently, the simulation results demonstrate the effectiveness of the LQR control method under the translational and rotational pushes of the wheel-legged system for human-robot interaction.

PID Sliding Mode Control of Prolate Flexible Pneumatic Actuators

2016 ◽  
Author(s):  
Jonathon E. Slightam ◽  
Mark L. Nagurka
Keyword(s):  
Sliding Mode Control ◽  
Position Control ◽  
Sliding Mode ◽  
Low Cost ◽  
Tracking Error ◽  
Pneumatic Actuators ◽  
Model Based ◽  
Mode Control ◽  
Significant Performance ◽  
Soft Actuators

The inherent compliance, high power-density, and musclelike properties of soft actuators are especially attractive and useful in many applications, including robotics. In comparison to classical/modern control approaches, model-based control techniques, e.g., sliding mode control (SMC), applied to flexible fluidic actuators (FFAs) offer significant performance advantages and are considered to be state-of-the-art. Improvements in position tracking are possible using nonlinear control approaches that offer enhanced performance for common applications such as tracking of sinusoidal trajectories at high frequencies. This paper introduces a SMC approach that increases the tracking capabilities of prolate flexible pneumatic actuators (PF-PAs). A model-based proportional, integral, derivative sliding mode control (PIDSMC) approach designed for position control of PFPAs is proposed. SMC and PIDSMC systems are implemented on low-cost open-source controls hardware and tested for tracking sinusoidal trajectories at frequencies of 0.5 Hz and 1.0 Hz with an amplitude of 8.255 mm and an offset of 12.7 mm. The PIDSMC approach reduced the maximum tracking error by 20.0%, mean error by 18.6%, and root-mean-square error by 10.5% for a 1 Hz sinusoidal trajectory and by 8.7%, 14.7%, and 3.8%, respectively, for a 0.5 Hz sinusoidal trajectory. These reductions in tracking errors demonstrate performance advantages of the PIDSMC over conventional sliding mode position controllers.

scholarly journals A Compact Soft Robotic Wrist Brace With Origami Actuators

2021 ◽  
Vol 8 ◽  
Author(s):  
Sicong Liu ◽  
Zhonggui Fang ◽  
Jianhui Liu ◽  
Kailuan Tang ◽  
Jianwen Luo ◽  
...  
Keyword(s):  
Wrist Joint ◽  
Low Cost ◽  
Ethylene Vinyl Acetate ◽  
Wearable Devices ◽  
Human Robot Interaction ◽  
Low Profile ◽  
Rehabilitation Devices ◽  
And Performance ◽  
Soft Actuators ◽  
Robotic Wrist

Wrist disability caused by a series of diseases or injuries hinders the patient’s capability to perform activities of daily living (ADL). Rehabilitation devices for the wrist motor function have gained popularity among clinics and researchers due to the convenience of self-rehabilitation. The inherent compliance of soft robots enabled safe human-robot interaction and light-weight characteristics, providing new possibilities to develop wearable devices. Compared with the conventional apparatus, soft robotic wearable rehabilitation devices showed advantages in flexibility, cost, and comfort. In this work, a compact and low-profile soft robotic wrist brace was proposed by directly integrating eight soft origami-patterned actuators on the commercially available wrist brace. The linear motion of the actuators was defined by their origami pattern. The extensions of the actuators were constrained by the brace fabrics, deriving the motions of the wrist joint, i.e., extension/flexion, ulnar/radial deviation. The soft actuators were made of ethylene-vinyl acetate by blow molding, achieving mass-production capability, low cost, and high repeatability. The design and fabrication of the soft robotic wrist brace are presented in this work. The experiments on the range of motion, output force, wearing position adaptivity, and performance under disturbance have been carried out with results analyzed. The modular soft actuator approach of design and fabrication of the soft robotic wrist brace has a wide application potential in wearable devices.

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