There is a strong demand for a human–machine-coexistent machine, e.g., a power-assist system or a computer-aided rehabilitation system, in the context of the super-aging society. In such a human–ma...

Haptics is a tactile feedback technology that recreates the sense of touch to the user by applying forces, vibrations, or motions. Haptic devices should have a high performance in their output characteristics, for example, low friction in off-state, constant force with constant input, and quick response with dynamic input, in order to generate a sufficient sense of touch to human skin. We have focused on rapid response of magnetorheological fluid and decided to use it as the working material of the haptic device. There are several types of magnetorheological fluids available, and the effects of the different types of magnetorheological fluids on the response time of the haptic device have not yet been reported. The objective of this study is to experimentally investigate the response time of a magnetorheological fluid–based haptic device with two different types of magnetorheological fluids. We originally developed a single-disc type magnetorheological fluid–based haptic device, and its response time was investigated with two types of magnetorheological fluids. We set three experimental conditions with regard to the fluid gap and rotational velocity. We modeled the haptic devices as a classic first-order lag system, and the time constant of this system was assumed to be representative of the response time of the haptic device. According to the results, the response times of a sample tend to be smaller with the narrow gap (0.1 mm), whereas those of the other tend to be smaller with the large gap (0.5 mm). In addition, the response time is non-dimensioned and investigated with Mason number.

Ankle-foot orthoses (AFOs) are orthotic devices that support the movement of the ankles of disabled people, for example, those suffering from hemiplegia or peroneal nerve palsy. We have developed an intelligently controllable AFO (i-AFO) in which the ankle torque is controlled by a compact magnetorheological fluid brake. Gait-control tests with the i-AFO were performed for a patient with flaccid paralysis of the ankles, who has difficulty in voluntary movement of the peripheral part of the inferior limb, and physical limitations on his ankles. By using the i-AFO, his gait control was improved by prevention of drop foot in the swing phase and by forward promotion in the stance phase.

In this study, we propose a leg-shaped robot (Leg-Robot) with a compact magnetorheological fluid clutch to demonstrate several kinds of haptic control of abnormal movements of brain-injured patient...

Magnetorheological fluids are composite materials made of ferromagnetic particles, medium oils, and several types of additives. We have developed actuation systems for the fine haptic control of master–slave robots. In this study, we proposed a new structure of a magnetorheological fluid–based actuator suitable for haptic devices. For the basic structure of the actuator, we proposed a twin-driven magnetorheological fluid actuator using two multi-layered disc-type magnetorheological fluid clutches for haptics. We conducted performance measures for the magnetorheological fluid clutches for haptics with three commercially available magnetorheological fluids (i.e. 122EG, 132DG, and 140CG from Lord Corp.). The experimental results show that 132DG is a better material for force control. Then, we proposed two types of twin-driven magnetorheological fluid actuators (i.e. link type and belt type) and compared their performance. The results show that the averages of the time constant are 19.1 and 16.1 ms for the link type and belt type, respectively. Furthermore, the averages of torque error are 0.033 and 0.068 N m for the link type and belt type, respectively. However, the belt-type twin-driven magnetorheological fluid actuator is better if a large range of motion is required, while the link-type twin-driven magnetorheological fluid actuator is better if accurate torque control is required.