Design and Development of Magneto-Rheological Actuators with Application in Mobile Robotics

In recent years, Magneto-Rheological (MR) fluids devices are widely studied and used for various purposes. Among these MR fluids devices, the MR actuator has attracted increasing attention for last two decades. An MR actuator is usually made of an active component (motor) and MR clutches. Compared with the regular actuators, the MR actuator features compliance due to the existence of MR fluids, which is commonly consider as benefits at the aspect of safety. On the other hand, the MR actuator has advantages on controllable bandwidth, torque-mass and torque-inertia ratios compared with the other compliant actuators. In this study, a new closed-loop, Field-Programable-Gate-Array (FPGA) based control scheme to linearize an MR clutch\u27s input-output relationship is presented. The feedback signal used in this control scheme is the magnetic field acquired from hall sensors within the MR clutch. The FPGA board uses this feedback signal to compensate for the nonlinear behavior of the MR clutch using an estimated model of the clutch magnetic field. The local use of an FPGA board will dramatically simplify the use of MR clutches for torque actuation. The effectiveness of the proposed technique is validated using an experimental platform that includes an MR clutch as part of a compliant actuation mechanism. The results clearly demonstrate that the use of the FPGA based closed-loop control scheme can effectively eliminate hysteretic behaviors of the MR clutch, allowing to have linear actuators with predictable behaviors. Moreover, a novel optimization design of MR clutches is proposed. Based on the optimization, the characteristics of MR clutches in three common configurations are discussed and compared. People can select suitable configuration of MR clutch before design. Lastly, a lightweight mobile robot is developed by using MR actuators. This mobile robot also has large driving force and can stop at any positions without running the motor

An Overview on Principles for Energy Efficient Robot Locomotion

Despite enhancements in the development of robotic systems, the energy economy of today's robots lags far behind that of biological systems. This is in particular critical for untethered legged robot locomotion. To elucidate the current stage of energy efficiency in legged robotic systems, this paper provides an overview on recent advancements in development of such platforms. The covered different perspectives include actuation, leg structure, control and locomotion principles. We review various robotic actuators exploiting compliance in series and in parallel with the drive-train to permit energy recycling during locomotion. We discuss the importance of limb segmentation under efficiency aspects and with respect to design, dynamics analysis and control of legged robots. This paper also reviews a number of control approaches allowing for energy efficient locomotion of robots by exploiting the natural dynamics of the system, and by utilizing optimal control approaches targeting locomotion expenditure. To this end, a set of locomotion principles elaborating on models for energetics, dynamics, and of the systems is studied

非線形弾性要素による内部力補償に基づく無段階変位–力変換機構の創生 ― 微小操作力で強大な磁気力・把持力・制動力・張力を制御可能とするロボット要素 ―

Tohoku University博士（情報科学）thesi

Design, Development, and Evaluation of Customized Electronics for Controlling a 5-DOF Magneto-Rheological Actuator Collaborative Robot

In recent years, Magneto-Rheological (MR) fluids has been used in various fields such as robotics, automotive, aerospace, etc. The most common use of the MR fluids is within a clutch-like mechanism, namely an MR clutch. When mechanical input is coupled to the input part of the MR clutch, the MR clutch provides a means of delivering this mechanical input to its output, through the MR fluids. The combination of the mechanical input device and the MR clutch is called an MR actuator. The MR actuator features inherently compliance owing to the characteristic of the MR fluids while also offering higher torque-to-mass and torque-to-inertia ratios over common actuators. As such, MR actuators are suitable candidates for human-safe and collaborative robots. The goal of this study is to design, develop and test customized electronic drivers that are compact and powerful to enable effective low-level control of the robot joints. The electronic drivers are responsible for sensor data processing, between-joint communication, supplying electric power, and executing control actions. The hardware design is optimized to handle transient current and voltage, and dissipate heat generated by components. Moreover, software development is based on μ C/OS-II real-time operating system to handle multiple time-critical tasks and to guarantee the stability and effectiveness of robot control system. A series of experiments are conducted to validate the designed hardware and software systems, and evaluate their performance

The design and control of an actively restrained passive mechatronic system for safety-critical applications

Development of manipulators that interact closely with humans has been a focus of research in fields such as robot-assisted surgery and haptic interfaces for many years. Recent introduction of powered surgical-assistant devices into the operating theatre has meant that robot manipulators have been required to interact with both patients and surgeons. Most of these manipulators are modified industrial robots. However, the use of high-powered mechanisms in the operating theatre could compromise safety of the patient, surgeon, and operating room staff. As a solution to the safety problem, the use of actively restrained passive arms has been proposed. Clutches or brakes at each joint are used to restrict the motion of the end-effector to restrain it to a pre-defined region or path. However, these devices have only had limited success in following pre-defined paths under human guidance. In this research, three major limitations of existing passive devices actively restrained are addressed. [Continues.

Multimodal series elastic actuator for human-machine interaction with applications in robot-aided rehabilitation

Series elastic actuators (SEAs) are becoming an elemental building block in collaborative robotic systems. They introduce an elastic element between the mechanical drive and the end-effector, making otherwise rigid structures compliant when in contact with humans. Topologically, SEAs are more amenable to accurate force control than classical actuation techniques, as the elastic element may be used to provide a direct force estimate. The compliant nature of SEAs provides the potential to be applied in robot-aided rehabilitation. This thesis proposes the design of a novel SEA to be used in robot-aided musculoskeletal rehabilitation. An active disturbance rejection controller is derived and experimentally validated and multiobjective optimization is executed to tune the controller for best performance in human-machine interaction. This thesis also evaluates the constrained workspaces for individuals experiencing upper-limb musculoskeletal disorders. This evaluation can be used as a tool to determine the kinematic structure of devices centred around the novel SEA