Hiroki Akai

Initial clinical tests for assessment models of synergy movements of stroke patients using PLEMO system with sensor grip device

In recent years, many researchers have studied on the rehabilitation robotics to assist medical staff or patients. Some kinds of haptic devices have been developed and evaluated its efficiency with clinical tests, for example, upper limb training for patients with spasticity after stroke. Almost all the devices for upper limb rehabilitation have only 2-DOF for its active motion except for wrists. But the upper limb of human works in 3-D space even except for the wrist; therefore designing a rehabilitation system for 3-D training is important. To meet this demand, we have developed a rehabilitation system for upper limbs, “PLEMO”. PLEMO is a kind of haptic device. However, in the previous system, we could not detect symptoms of abnormal movement of patients, for example synergy patterns of stroke patients, because of a lack of sensors. In this paper, we developed new sensing device for detecting such abnormal symptoms. The purpose of this study is to build an appropriate evaluation system for stroke patients with such information of abnormal symptoms. As a first step, we conducted reaching/pulling tests with this device. In this clinical evaluation, the subject is six stroke patients with different Brunnstrom stages (3, 4, 5) and twenty seven healthy subjects. By comparison with a patient movement (stage 3, 4, 5) and a normal movement, we recognized some differences of gripping forces, grip rotation angle and ground reaction forces among their movements.

Study on development of active-passive rehabilitation system for upper limbs: Hybrid-PLEMO

In recent years, many researchers have studied the potential of using robotics technology to assist and quantify the motor functions for neuron-rehabilitation. Some kinds of haptic devices have been developed and evaluated its efficiency with clinical tests, for example, upper limb training for patients with spasticity after stroke. Active-type (motor-driven) haptic devices can realize a lot of varieties of haptics. But they basically require high-cost safety system. On the other hand, passive-type (brake-based) haptic devices have inherent safety. However, the passive robot system has strong limitation on varieties of haptics. There are not sufficient evidences to clarify how the passive/active haptics effect to the rehabilitation of motor skills. In this paper, we developed an active-passive-switchable rehabilitation system with ER clutch/brake device named Hybrid-PLEMO in order to address these problems. In this paper, basic structures and haptic control methods of the Hybrid-PLEMO are described.

“Hybrid-PLEMO”, rehabilitation system for upper limbs with active / passive force feedback mode

Several rehabilitation robots for upper limbs have been proposed so far, and clinical effectiveness was reported in several studies for the aged people or patients with stroke. However most of them have only 2-DOF for its active motion. It is important for designing a rehabilitation system which trains in the 3-DOF space because the upper limbs of humans works in 3-DOF space even expect for the wrist. We developed the quasi 3-DOF rehabilitation system which has 2-DOF force-feedback function in working plane but its working plane can be adjusted the inclination. And we named it Hybrid-PLEMO for it can be switched between active type and passive type. Hybrid-PLEMO is a compact, low-cost rehabilitation system for upper limbs with high safety by using ER brakes or ER actuators. Additionally, in Hybrid-PLEMO, we take direct-drive linkage mechanism by adding sub links. In this paper, we describe the mechanism and haptic control of Hybrid-PLEMO.

“Hybrid-PLEMO“, rehabilitation system for upper limbs with active / passive force feedback, and its application for facilitation techniques

Many kinds of actuator-based (active type) haptic devices have developed and utilized as rehabilitation robots. These systems have great advantages for rehabilitative activities, for example assistive forces and so on. However, from the view point of safety, we have a room to consider utilizing brake-based (passive type) haptic devices as rehabilitation-tools. The effects and roles of active / passive force feedback for rehabilitative effects have not been clarified yet. Since a few years ago, we have developed an active / passive switchable rehabilitation system for upper limbs (Hybrid-PLEMO) to address these questions. In this paper, we describe force-feedback mechanism of the Hybrid-PLEMO. Then, we suggest a new approach to facilitate a human reaching motion with our system. As a specific method, we decided to utilize an oscillatory stimulation. We discuss the role and limitation of the active / passive oscillatory stimulation as a facilitation force for human reaching motion.

A performance evaluation method of a passive type force display and rehabilitation system with redundant brakes

We developed a compact and low-cost quasi-3-DOF rehabilitation system “Hybrid-PLEMO” for upper limbs of stroke patients. Hybrid-PLEMO has 2-DOF force feedback function in working plane, its working plane can be adjusted the inclination, and it can be switched between active type and passive type. However, there are some directions and link positions which are difficult to display the force when Hybrid-PLEMO works at passive type. Redundant brakes method had been suggested to made it possible to display various force directions and various postures of virtual objects by the improvement of the controllability. In this paper, a novel method is presented for performance evaluation of a passive-type force display system with redundant brakes. Using this method, we evaluate the performance of a 2-DOF passive-type force display system with and without redundant brakes, and draw a conclusion that it is good to add redundant brakes to the passive-type force display and rehabilitation system.