The cascade impedance control (CIC) is a wellknown architecture framework for rehabilitation exoskeleton with compliant joint (e.g., a series elastic actuator). The cascaded position-torque-velocity control loop of the CIC system can deal with specific issues, such as stiction or the accuracy of output impedance. In this paper, the control loops of the CIC are extended by the traditional iterative learning control (ILC), and then we examine and compare three types of frameworks, named torque learning, impedance learning, and trajectory learning. Their advantages, such as reducing the lag of the output trajectory with a low-gain impedance controller (safety), are discovered. Furthermore, the exoskeleton system is upgraded with the ability of a variable impedance. In this part, a fuzzy logic system is proposed. This system employs the electromyography signals of the subject and the exoskeleton torque as input, and the decisions on the variable impedance as output. The experiment verifies that the proposed algorithm can effectively decrease the impedance of the exoskeleton when detecting a spasticity from the subject, and can maintain the original dynamics of the system when the subject performs a normal movement. Afterwards, the effectiveness of the fuzzy logic system together with the ILC-based CIC is experimentally verified in the case of subject-exoskeleton collaborative. 

Iterative Learning Control for Cascaded Impedance-Controlled Compliant Exoskeleton with Adaptive Reaction to Spasticity

The steering trapezoid designed according to the Ackermann steering geometry potentially causes excessive tire wear and affects the steering performance due to the large tire deformation resulting ...

https://journals.sagepub.com/doi/pdf/10.1177/1754337119872417

Research on race car steering geometry considering tire side slip angle

Kinematic and Structural Analysis of Independent type suspension system with Anti-Roll bar for Formula Student Vehicle

This work proposes a novel contactless sensor to measure the micro torque of a rotating shaft based on the optical coherence displacement measurement (OCDM) principle. The experimental system features a simple mechanical testing system to measure the torque, a calibration device to establish the measurement baseline, and a polyetheretherketone (PEEK) shaft to improve the theoretical resolution of the system up to 0.003 Nm. The torque measurement results indicate that this sensor achieved a maximum nonlinearity error of 0.0484 %, maximum repeatability error of 0.2771 %, and maximum hysteresis error of 0.2252 %. This high accuracy of our system stems from the use of high-precision optical principles and the novel physical mapping of the torque (i.e., processing scales on the shaft surface to represent the twist angle by designing a laser engraving system) capable of resisting the negative effects of radial vibrations. Additionally, our torque measurement sensor possesses broader applicability by effectively resisting the impacts of temperature variations and electromagnetic interference. These attributes make it excel other torque sensors presented in the literature in recent years. 

Novel contactless torque sensor based on optical coherence

This paper proposes a novel index finger exoskeleton with semi-wrapped fixtures and elastomer-based clutched series elastic actuators. The semi-wrapped fixture is similar to a clip, which improves the convenience of donning/doffing and connection stability. The elastomer-based clutched series elastic actuator can limit the maximum transmission torque and improve passive safety. Second, the kinematic compatibility of the exoskeleton mechanism for the proximal interphalangeal joint is analyzed, and its kineto-statics model is built. To avoid the damage caused by the force along the phalanx, considering the individual difference in the size of the finger segment, a two-level optimization method is proposed to minimize the force along the phalanx. Finally, the performance of the proposed index finger exoskeleton is tested. Statistical results indicate that the donning/doffing time of the semi-wrapped fixture is significantly less than that of the Velcro. Compared with the Velcro, the average value of the maximum relative displacement between the fixture and the phalanx is reduced by 59.7%. Compared with the exoskeleton before optimization, the maximum force along the phalanx generated by the exoskeleton after optimization is reduced by 23.65%. The experimental results show that the proposed index finger exoskeleton can improve the convenience of donning/doffing, connection stability, comfort, and passive safety. 

Design and Optimization of an Index Finger Exoskeleton with Semi-Wrapped Fixtures and Series Elastic Actuators

Elastic torque sensors have been widely used for small-scale robots such as hand exoskeletons to achieve torque control. However, designing a miniaturized and lightweight elastic torque sensor with human–machine interaction safety is still a challenge. In this article, a novel miniaturized and lightweight elastomer-based clutched torque sensor is presented. A rubber spring is designed and used to reduce its volume and weight. A wafer disk clutch is devised to improve mechanical safety. The torque sensor is 29.5 mm $\times18$ mm $\times24$ mm in dimension and weighs 23 g. Compared with the state-of-the-art elastic torque sensors for hand exoskeletons, the volume-to-torque ratio is reduced by 15.48%, and its weight is reduced by 23.33%. Since the hysteresis characteristics of the rubber spring leads to a nonlinear deformation–torque relationship, an improved parametric Gaussian process regression (PGPR) method based on the nonlinear autoregressive moving average structure with exogenous inputs (NARMAX) is proposed. A combined kernel function for the improved PGPR is designed to improve the fitting performance. Finally, experiments have been conducted to verify the mechanical safety and torque sensing performance. The force caused by collision on the proposed torque sensor is less than that on the torque sensor without the clutch (reduced by 51.78%). The proposed hysteresis model can reduce the maximum absolute modeling error to 7% compared with those of other intelligent hysteresis models (the modeling error is 12.32%). Therefore, the experimental results indicate that the proposed torque sensor can improve the mechanical safety and achieve accurate torque sensing.

Design and Hysteresis Modeling of a Miniaturized Elastomer-Based Clutched Torque Sensor

In this paper, FSAE race car is taken as the research object, dynamic performance of the suspension system is studied. 3D model of the whole vehicle suspension system is built by using 3D modeling software, and the kinematics simulation is carried out. On the basis of this, ADAMS is used for dynamic simulation, the changes of kingpin inclination angle, kingpin caster angle, camber angle, front wheel toe angle and ground point lateral slip amount of front wheel with wheel beat is analyzed, and the outer wheel angle has been optimized and designed. The results show that the designed suspension system meets the design requirements.

Design and Optimization of FSAE Race Car suspension system

This paper presents a miniaturized equipment used in tracking and pointing, and provides a method for free space optical communication among small platform. This scheme uses simple scan mirror and receiver with single photo detector to achieve tracking function. Signal beacon is controlled to rotate around target receiver. Transmitter constantly adjusts emitting direction to track receiver according to received signal intensity, which is send back by reverse laser link. The prototype system is successfully established and its transmitting part consisted by directly modulated laser diode, mechanical collimation lens, and scan mirror is also proved. The receiving end is mainly composed of large area photo detector and short-focal lens. Field-programmable gate array chips set in both ends are used to implement tracking algorithm. This system can track target at speed of 40 mm/s within 2 m distance in an angle range of ±30°. For further application, the system has great potential for miniaturization because of elimination of motors, beacons and cameras in its scheme.

Self-Alignment FSOC System With Miniaturized Structure for Small Mobile Platform

This paper proposes a novel index finger exoskeleton with semi-wrapped fixtures and elastomer-based clutched series elastic actuators. The semi-wrapped fixture is similar to a clip, which improves the convenience of donning/doffing and connection stability. The elastomer-based clutched series elastic actuator can limit the maximum transmission torque and improve passive safety. Second, the kinematic compatibility of the exoskeleton mechanism for the proximal interphalangeal joint is analyzed, and its kineto-statics model is built. To avoid the damage caused by the force along the phalanx, considering the individual difference in the size of the finger segment, a two-level optimization method is proposed to minimize the force along the phalanx. Finally, the performance of the proposed index finger exoskeleton is tested. Statistical results indicate that the donning/doffing time of the semi-wrapped fixture is significantly less than that of the Velcro. Compared with the Velcro, the average value of the maximum relative displacement between the fixture and the phalanx is reduced by 59.7%. Compared with the exoskeleton before optimization, the maximum force along the phalanx generated by the exoskeleton after optimization is reduced by 23.65%. The experimental results show that the proposed index finger exoskeleton can improve the convenience of donning/doffing, connection stability, comfort, and passive safety.

Design and Optimization of an Index Finger Exoskeleton With Semi-Wrapped Fixtures and Series Elastic Actuators

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Papers

Design and Hysteresis Modeling of a Miniaturized Elastomer-Based Clutched Torque Sensor

Design and Optimization of FSAE Race Car suspension system

Self-Alignment FSOC System With Miniaturized Structure for Small Mobile Platform

Design and Optimization of an Index Finger Exoskeleton With Semi-Wrapped Fixtures and Series Elastic Actuators