Nobuhiro Ushimi

Rehabilitation robots assisting in walking training for SCI patient

We have been developing a series of robots to apply for each step of spinal cord injury (SCI) recovery. We describe the preliminary walking pattern assisting robot and the practical walking assisting robot, which will be applied to the incomplete type of SCI to Quadriplegia. The preliminary experimental results are performed by normal subjects to verify the basic functions of the robot assisting and to prepare the test by SCI patients.

Rehabilitation Robot in Primary Walking Pattern Training for SCI Patient at Home

Recently, attention has been focused on incomplete-type spinal cord injury to the central spine caused by pressure on parts of the white matter conducting pathway such as the pyramidal tract. In this paper, we focus on a training robot designed to assist with primary walking pattern training. The target patient of this training robot is one who is relearning the basic functions of the usual walking pattern, especially for patients with the incomplete type SCI to the central spine, who are capable of standing by themselves but are not capable of performing walking motions. From the perspective of human engineering, we monitored the operator’s actions to the robot and investigated the movement of joints of the lower extremities, the circumference of the lower extremities and the exercise intensity with the machine. The concept of the device is to provide mild training without any sudden changes in heart rate or blood pressure, which will be particularly useful for the elderly and disabled.

Vibration suppression control for multiaxis table drive system

This paper presents new vibration suppression control method for multiaxis table drive system. In multiaxis table drive system, the synchronization error disturbs high precision and a fast response time to cause serious vibration. It is caused by a motion error due to a characteristics change of a table slide system. In the case of synchronization error suppression, the model of motion characteristics of a table slide system is necessary and the time delay in a servo controller has to compensate. The proposed method consists of two steps. The first step is the identification of moment of load inertia, viscous friction coefficient and coulomb friction for each axis in an independent state by offline identification method to make a table slide system. The second step is new predictive synchronization error compensation algorithm (PSEC) to reject of the transfer delay time influence of servo controller in a state with the axis interference. PSCA is designed by using synchronization torque error, velocity error and position error. The proposed method is verified by the simulations and the experimental results that PSEC is robust as compared to the without predictive function on the twin axes drive system.

Nonlinear friction compensation for a high precision stage using synchronous piezoelectric device driver

In the machine tool industry and the semiconductor manufacture fields, the necessity of high precision and fast response is rapidly spreading. In general, it is well known that a positioning control system contains nonlinear friction force; it may cause a serious disadvantage on control performances such as tracking errors, limit cycles and undesired stick-slip motion at very low motion velocity. In order to achieve the high level control performance, the frictional effects have to be removed. This paper presents a novel nonlinear friction compensation approach based on the idea of P,PI/I-P+FF control with sliding mode compensator for a high precision stage using a synchronous piezoelectric device driver. P,PI/I-P+FF control consists of Proportional position control and Proportional-Integral/Integral-Proportional velocity control with velocity Feed-Forward compensator. Experimental results are given to show the effectiveness of our proposed control method compared to the conventional P,PI/I-P+FF control method. Especially, the positioning error of our proposed control was reduced by more than 2/3 compared to the case of the conventional control at a stepping motion.

A study of a standing-up motion training aid by non-electric source driving

Standing-up motion training has been practiced as a highly effective rehabilitation for strengthening lower limb muscles by Physical Therapist in hospitals and the like. Meanwhile, elderly persons and patients with recovery tendency desire to execute this standing-up motion training at ordinary households. In this paper, we develop a simple type of a standing-up motion training aid for cordless and non-electric source driving uses in order to repeat standing-up motions by a simple mechanism.

Rehabilitation robot in primary walking pattern training for SCI patient: Training robot for home-use based on the experiments of the hospital-use type

Recently, attention has been focused on incomplete-type spinal cord injury (SCI) to the central spine caused by pressure on parts of the white matter conducting pathway such as the pyramidal tract. In this paper, we focus on a training robot designed to assist with primary walking pattern training. The target patient of this training robot is one who is relearning the basic functions of the usual walking pattern, especially for patients with the incomplete type SCI to the central spine, who are capable of standing by themselves but are not capable of performing walking motions. We investigated the movement of joints of the lower extremities, the circumference of the lower extremities and the exercise intensity with the machine. From the experimental results the training robot for home-use based on the experiments on the hospital-use type is proposed. The operating panel, accessibility from wheel chair to the robot and the mechanism were modified for the home-use.

Vibration suppression compensator using nonlinear observer for table positioning systems

To achieve high-speed, high-precision position control for semiconductor product machines and industrial robots, full-closed feedback control is applied. Many control methods have been proposed for such a system. In general, proportional position control and proportional plus integral velocity control or integral plus proportional velocity control (P, PI/I-P), which is a type of proportional plus integral plus deferential control (PID), is applied in many industrial applications. However, in the case of changing mechanical characteristics of the control target, the parameters of P, PI/I-PI control must also change or a disturbance observer is applied, to maintain good motion performance. In this paper, we propose a nonlinear observer to suppress the vibration for a table positioning system. The algorithm of the nonlinear observer is based on sliding mode control with chattering compensation. The effectiveness of the proposed observer is evaluated using a full-closed 2mass system model via point-to-point control in the case of changing load. The simulations and experiments indicate that the proposed observer is effective for vibration suppression in the case of changing load.