Research

14 pages, 7382 KiB

Open AccessArticle

Adaptive Control of Chaotic Signals: Investigated by Simulation Software and Real Electronic Circuits

by Cheng-Hsiung Yang, Che-Lun Chang and Shih-Yu Li

Actuators 2021, 10(11), 284; https://0-doi-org.brum.beds.ac.uk/10.3390/act10110284 - 25 Oct 2021

Cited by 1 | Viewed by 1952

Chaotic behavior is complicated, sensitive, and has the feature of great variety, which are the most potential signals to be applied in data encryption, secure communication, medical information protection, etc. As a consequence, in this paper, we try to propose three different ways [...] Read more.

Chaotic behavior is complicated, sensitive, and has the feature of great variety, which are the most potential signals to be applied in data encryption, secure communication, medical information protection, etc. As a consequence, in this paper, we try to propose three different ways to show our data generating results step by step, which means it can be proved effectively and used in practice: (1) Chaotic solutions simulated by MATLAB, (2) chaotic motion drawn via electronic circuits software Multisim, and (3) chaotic signal implemented on real electronic circuits with breadboard. In advance, following the same design principal, the adaptive chaotic signal is also designed and presented in the end of this article for further study, which provides a more flexible and variable chaotic signal to enhance the encryption effectiveness. The experimental results are extremely close to the two simulation results and can definitely be technically transferred to real encryption application. Full article

(This article belongs to the Special Issue Actuators in Robotic Control)

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13 pages, 2855 KiB

Open AccessArticle

Investigation of Hysteresis Effect in Torque Performance for a Magnetorheological Brake in Adaptive Knee Orthosis

by Yaojung Shiao and Premkumar Gadde

Actuators 2021, 10(10), 271; https://0-doi-org.brum.beds.ac.uk/10.3390/act10100271 - 15 Oct 2021

Cited by 5 | Viewed by 2483

Abstract

Semi-active knee orthosis (SAKO) is a kind of wearable lower-limb exoskeleton that uses actuators to support the regular biomechanical functions. It is much better than conventional knee orthosis (CKO) devices because of its high torque to volume ratio (TVR) and low mass. Magnetorheological [...] Read more.

Semi-active knee orthosis (SAKO) is a kind of wearable lower-limb exoskeleton that uses actuators to support the regular biomechanical functions. It is much better than conventional knee orthosis (CKO) devices because of its high torque to volume ratio (TVR) and low mass. Magnetorheological (MR) brake is one of the smart actuators that can be used as an active resistance device in SAKO. It has advantages of fast response, low power consumption, and low vibration operation. This smart brake also has wide applications in the robotic and automotive industries. However, the electromagnetic setup in MR brakes has a hysteresis problem. This paper aims to turn this hysteresis problem into an advantage to save the power consumption of MR brake. Since the SAKO needs precise torque control, this research studied the hysteresis effect on the torque performance of MR brake. A less energy-consuming PWM actuation signal is proposed to activate the MR brake. The effects of frequency and duty cycle of PWM actuation signal on MR brake performance are also investigated. The electromagnetic (EM) and mechanical models of the MR brake were developed to simulate performance. Initial validation of these models is done by simulating the MR brake model with the DC actuation signal in finite element analysis software. For the final validation, the model simulation results are compared with experimental results. The factors affecting the steady torque and the response time of the MR brake are studied to find the optimal frequency and duty cycle for the applied PWM signal. This study revealed that the proposed new PWM actuation signal with a 5 kHz frequency and 60% duty cycle can power the MR brake to maintain steady torque. By turning hysteresis into an advantage, it saves 40% power consumption of MR brake compared to DC signal. Full article

(This article belongs to the Special Issue Actuators in Robotic Control)

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18 pages, 1858 KiB

Open AccessArticle

Port-Hamiltonian Modeling and IDA-PBC Control of an IPMC-Actuated Flexible Beam

by Weijun Zhou, Yongxin Wu, Haiqiang Hu, Yanjun Li and Yu Wang

Actuators 2021, 10(9), 236; https://0-doi-org.brum.beds.ac.uk/10.3390/act10090236 - 14 Sep 2021

Cited by 7 | Viewed by 2650

Abstract

In this paper, the infinite-dimensional port-Hamiltonian modelling and control problem of a flexible beam actuated using ionic polymer metal composite (IPMC) actuators is investigated. The port-Hamiltonian framework is used to propose an interconnected control model of the mechanical flexible beam and the IPMC [...] Read more.

In this paper, the infinite-dimensional port-Hamiltonian modelling and control problem of a flexible beam actuated using ionic polymer metal composite (IPMC) actuators is investigated. The port-Hamiltonian framework is used to propose an interconnected control model of the mechanical flexible beam and the IPMC actuator. The mechanical flexible dynamic is modelled as a Timoshenko beam, and the electric dynamics of the IPMCs are considered in the model. Furthermore, a passivity-based control-strategy is used to obtain the desired configuration of the proposed interconnected system, and the closed-loop stability is analyzed using the early lumped approach. Lastly, numerical simulations and experimental results are presented to validate the proposed model and the effectiveness of the proposed control law. Full article

(This article belongs to the Special Issue Actuators in Robotic Control)

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20 pages, 7293 KiB

Open AccessArticle

Design and Implementation of a Robotic Hip Exoskeleton for Gait Rehabilitation

by Shi-Heng Hsu, Chuan Changcheng, Heng-Ju Lee and Chun-Ta Chen

Actuators 2021, 10(9), 212; https://0-doi-org.brum.beds.ac.uk/10.3390/act10090212 - 29 Aug 2021

Cited by 8 | Viewed by 4622

Abstract

In this paper, a four degrees-of-freedom robotic hip exoskeleton was proposed for gait rehabilitation. The robotic hip exoskeleton was designed with active flexion/extension and passive abduction/adduction at each hip joint to comply with the movement of the thigh. Due to each user’s different [...] Read more.

In this paper, a four degrees-of-freedom robotic hip exoskeleton was proposed for gait rehabilitation. The robotic hip exoskeleton was designed with active flexion/extension and passive abduction/adduction at each hip joint to comply with the movement of the thigh. Due to each user’s different lower limbs characteristics and unknown torques at hip joints, model-free linear extended state observer (LESO)-based controllers were proposed for rehabilitation gait control. The prototypes of the robotic hip exoskeleton and controller designs were validated and compared through walking and ascending rehabilitation experiments. Additionally, a motion captured system and EMG signals were used to investigate the walking assistance of the robotic hip exoskeleton. Full article

(This article belongs to the Special Issue Actuators in Robotic Control)

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15 pages, 3067 KiB

Open AccessArticle

MCI Detection Using Kernel Eigen-Relative-Power Features of EEG Signals

by Yu-Tsung Hsiao, Chia-Fen Tsai, Chien-Te Wu, Thanh-Tung Trinh, Chun-Ying Lee and Yi-Hung Liu

Actuators 2021, 10(7), 152; https://0-doi-org.brum.beds.ac.uk/10.3390/act10070152 - 04 Jul 2021

Cited by 7 | Viewed by 2939

Abstract

Classification between individuals with mild cognitive impairment (MCI) and healthy controls (HC) based on electroencephalography (EEG) has been considered a challenging task to be addressed for the purpose of its early detection. In this study, we proposed a novel EEG feature, the kernel [...] Read more.

Classification between individuals with mild cognitive impairment (MCI) and healthy controls (HC) based on electroencephalography (EEG) has been considered a challenging task to be addressed for the purpose of its early detection. In this study, we proposed a novel EEG feature, the kernel eigen-relative-power (KERP) feature, for achieving high classification accuracy of MCI versus HC. First, we introduced the relative powers (RPs) between pairs of electrodes across 21 different subbands of 2-Hz width as the features, which have not yet been used in previous MCI-HC classification studies. Next, the Fisher’s class separability criterion was applied to determine the best electrode pairs (five electrodes) as well as the frequency subbands for extracting the most sensitive RP features. The kernel principal component analysis (kernel PCA) algorithm was further performed to extract a few more discriminating nonlinear principal components from the optimal RPs, and these components form a KERP feature vector. Results carried out on 51 participants (24 MCI and 27 HC) show that the newly introduced subband RP feature showed superior classification performance to commonly used spectral power features, including the band power, single-electrode relative power, and also the RP based on the conventional frequency bands. A high leave-one-participant-out cross-validation (LOPO-CV) classification accuracy 86.27% was achieved by the RP feature, using a simple linear discriminant analysis (LDA) classifier. Moreover, with the same classifier, the proposed KERP further improved the accuracy to 88.24%. Finally, cascading the KERP feature to a nonlinear classifier, the support vector machine (SVM), yields a high MCI-HC classification accuracy of 90.20% (sensitivity = 87.50% and specificity = 92.59%). The proposed method demonstrated a high accuracy and a high usability (only five electrodes are required), and therefore, has great potential to further develop an EEG-based computer-aided diagnosis system that can be applied for the early detection of MCI. Full article

(This article belongs to the Special Issue Actuators in Robotic Control)

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16 pages, 4782 KiB

Open AccessArticle

Develop Real-Time Robot Control Architecture Using Robot Operating System and EtherCAT

by Wei-Li Chuang, Ming-Ho Yeh and Yi-Liang Yeh

Actuators 2021, 10(7), 141; https://0-doi-org.brum.beds.ac.uk/10.3390/act10070141 - 24 Jun 2021

Cited by 7 | Viewed by 5834

Abstract

This paper presents the potential of combining ROS (Robot Operating System), its state-of-art software, and EtherCAT technologies to design real-time robot control architecture for human–robot collaboration. For this, the advantages of an ROS framework here are it is easy to integrate sensors for [...] Read more.

This paper presents the potential of combining ROS (Robot Operating System), its state-of-art software, and EtherCAT technologies to design real-time robot control architecture for human–robot collaboration. For this, the advantages of an ROS framework here are it is easy to integrate sensors for recognizing human commands and the well-developed communication protocols for data transfer between nodes. We propose a shared memory mechanism to improve the communication between non-real-time ROS nodes and real-time robot control tasks in motion kernel, which is implemented in the ARM development board with a real-time operating system. The jerk-limited trajectory generation approach is implemented in the motion kernel to obtain a fine interpolation of ROS MoveIt planned robot path to motor. EtherCAT technologies with precise multi-axis synchronization performance are used to exchange real-time I/O data between motion kernel and servo drive system. The experimental results show the proposed architecture using ROS and EtherCAT in hard real-time environment is feasible for robot control application. With the proposed architecture, a user can efficiently send commands to a robot to complete tasks or read information from the robot to make decisions, which is helpful to reach the purpose of human–robot collaboration in the future. Full article

(This article belongs to the Special Issue Actuators in Robotic Control)

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18 pages, 1232 KiB

Open AccessArticle

A Robust Noise-Free Linear Control Design for Robot Manipulator with Uncertain System Parameters

by Yi-Liang Yeh

Actuators 2021, 10(6), 121; https://0-doi-org.brum.beds.ac.uk/10.3390/act10060121 - 05 Jun 2021

Cited by 4 | Viewed by 2325

Abstract

In robot control, the sliding mode control is known for its robustness against external disturbances and system uncertainties. However, it has the disadvantage of control chattering, which can damage the actuator and degrade system performance. With a new stability proof, this paper presents [...] Read more.

In robot control, the sliding mode control is known for its robustness against external disturbances and system uncertainties. However, it has the disadvantage of control chattering, which can damage the actuator and degrade system performance. With a new stability proof, this paper presents an alternative simple linear feedback control that can cope with large system uncertainties and suppress large external disturbances, doing so as effectively as sliding mode control does. The advantage of using linear control is that the control law is simple and control chattering can be avoided. Moreover, a noise-free control scheme is proposed as an improvement of the feedback control; the modified design preserves the advantages of linear control and generates a chattering-free control signal even in a noisy environment. Full article

(This article belongs to the Special Issue Actuators in Robotic Control)

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19 pages, 593 KiB

Open AccessArticle

Output Feedback Tracking Sliding Mode Control for Systems with State- and Input-Dependent Disturbances

by Yi-Liang Yeh

Actuators 2021, 10(6), 117; https://0-doi-org.brum.beds.ac.uk/10.3390/act10060117 - 31 May 2021

Cited by 5 | Viewed by 2688

Abstract

In this paper, output feedback tracking sliding mode control was considered for uncertain multivariable linear systems. The uncertainties included external disturbance, the system state, and control input. A new property of the loop transfer recovery (LTR) observer was first established: the state estimation [...] Read more.

In this paper, output feedback tracking sliding mode control was considered for uncertain multivariable linear systems. The uncertainties included external disturbance, the system state, and control input. A new property of the loop transfer recovery (LTR) observer was first established: the state estimation error of the LTR observer can be made arbitrarily small with respect to state- and input-dependent system uncertainties. Observer-based output feedback tracking sliding mode control using the LTR observer is presented. The proposed sliding mode control approach can maintain the boundedness of the system state and drive the system outputs arbitrarily close to the desired reference outputs; the degree of closeness was determined by a design parameter in the LTR observer. In the proposed approach, the most general and simple observer-based output feedback control formulation was used to achieve global tracking. Simulations with a two-degree-of-freedom (DOF) robotic manipulator application illustrated the claimed properties, and a peaking and chattering reduction technique was demonstrated to protect the actuator. Full article

(This article belongs to the Special Issue Actuators in Robotic Control)

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18 pages, 3718 KiB

Open AccessArticle

Tracking Control of Pneumatic Artificial Muscle-Activated Robot Arm Based on Sliding-Mode Control

by Chih-Jer Lin, Ting-Yi Sie, Wen-Lin Chu, Her-Terng Yau and Chih-Hao Ding

Actuators 2021, 10(3), 66; https://0-doi-org.brum.beds.ac.uk/10.3390/act10030066 - 22 Mar 2021

Cited by 16 | Viewed by 3896

Abstract

This study discusses a circular trajectory tracking function through a proposed pneumatic artificial muscle (PAM)-actuated robot manipulator. First, a dynamic model between a robot arm and a PAM cylinder is introduced. Then the parameters thereof are identified through a genetic algorithm (GA). Finally, [...] Read more.

This study discusses a circular trajectory tracking function through a proposed pneumatic artificial muscle (PAM)-actuated robot manipulator. First, a dynamic model between a robot arm and a PAM cylinder is introduced. Then the parameters thereof are identified through a genetic algorithm (GA). Finally, PID is used along with a high-order sliding-mode feedback controller to perform circular trajectory tracking. As the experimental results show, the parameters of sampling time and moment of inertia are set to accomplish the trajectory tracking task in this study. In addition, the maximum error between the objective locus and the following locus was 11.3035 mm when applying theta-axis control to the circular trajectory of the robot arm with zero load or lower load. In an experiment of controller comparison, the results demonstrate that a high-order sliding-mode feedback controller is more robust in resisting external interference and the uncertainty of modeling, making the robot arm have good performance when tracking. Full article

(This article belongs to the Special Issue Actuators in Robotic Control)

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