The aim of this study was to establish a control system with multi-axis motors for a lower limb robotic exoskeleton (LLRE). Methods This LLRE structure was built by using an aluminum alloy designed with an adjustable mechanism. A fourmotor control system with four Maxon brushless direct current motors was developed and installed in the hips and knees of the LLRE, respectively. In addition, four harmonic reducers were connected to the motors to increase the torque. A master controller which commands the four-axis motors was developed by using Texas Instruments (TI) embedded chip (TMS320F28069). The walking gait parameters were established to support the LLRE movement. The controller local area network protocol was used to communicate between the master and slave motor controllers. The slave motor controllers were developed by using TI embedded chip (DRV8301/TMS320F28069) for each joint by a high bandwidth control strategy. A high dynamic response system was obtained by considering the LLRE inertia, external variable load induced by the LLRE and delay in a digital control system. Results The result showed that this high bandwidth control with the experimental ones, the trajectory of each joint demonstrated a high response bandwidth and the tracking gait errors were significantly eliminated. Conclusions This study indicated that the development of this LLRE with a master controller/the slave motor controllers strategy through controller local area network protocol was feasible for healthcare applications.

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This paper developed a rotatable multi-axis motion platform combined with virtual reality (VR) immersion for flight simulation purposes. The system could simulate the state of the flight operation. The platform was mainly comprised of three crank linkage mechanisms to replace an expensive six degrees of freedom (DoF) Stewart platform. Then, an independent subsystem which could rotate ±180° was installed at the center of the platform. Therefore, this platform exhibited 4-DoF movement, such as heave, roll, pitch, and yaw. In the servo motor control unit, Visual Studio C# was applied as the software to establish a motion control system to interact with the motion controller and four sets of servo motors. Ethernet Control Automation Technology (EtherCAT) was utilized to communicate the commands and orders between a PC and each servo motor. The optimum controller parameters of this system were obtained using Simulink simulation and verified by experiment. The multiple sets of servo motors and crank linkage mechanisms were synchronized with flight VR imagery. For VR imagery, the software Unity was used to design the flying digital content. The controller was used to transmit the platform’s spatial information to meet the direction of the pilot commands and to compensate the direction of the deviation in spatial coordinates. To achieve synchronized response and motion with respect to the three crank linkage mechanism platform and VR imagery on the tester’s goggle view, the relation of the spatial coordinate of VR imagery and three crank linkage mechanisms was transformed to angular displacement, speed and acceleration which were used to command the motor drive system. As soon as the position of the VR imagery changed, the computer instantly synchronized the VR imagery information to the multi-axis platform and performed multi-axis dynamic motion synchronously according to its commanded information. The testers can thus immerse in the VR image environment by watching the VR content, and obtain a flying experience.

This study presents a misalignment light-guiding module to increase the effectiveness of absorbing light. For a general fixed-type photovoltaic (PV) panel, the misalignment light decreases the efficiency of the system. A solar tracking system was installed for obtaining higher power generation. However, the cost of the PV system and maintenance was 5–10 times higher than the general type. In this study, this module is composed of an array of misalignment light-guiding units that consist of a non-axisymmetric compound parabolic curve (NACPC) and a freeform surface collimator. The NACPC efficiently collects the misalignment light within ±30° and guides the light to the collimator. The light has a better uniformity and smaller angle at the exit aperture. The simulation results show that the optical efficiency of the unit was above 70% when the misalignment angle was smaller than 20°. The experimental results show that the power generation of the light-guiding unit was 1.8 times higher than the naked PV panel.