Saku Egawa

Power-assisted walking support system for elderly

This system is to support elderly people who need some help in standing up from the bed, walking around, sitting down to the toilet or bed for rehabilitation. In the design of this system, the use of the left function of the user was strongly considered. The experimental mechanism of the walking support system is developed. The basic features are: (1) electrically power-assisted in both motions of standing-up/sitting-down and walking; (2) a sensor system for easier motion instruction for the elderly. Future research includes field test and evaluation of the system functions. The force sensitive motion control method with compensation of gravity on the slope is also discussed.

Dual excitation multiphase electrostatic drive

A novel electrostatic drive technology, named the dual excitation multiphase electrostatic drive (DEMED) is presented. A basic DEMED consists of two plastic films in which three-phase parallel electrodes are embedded and is driven by three-phase AC excitation to the electrodes. Static characteristics of DEMED are calculated and tested and the results agree very well. Three prototype motors of DEMED are fabricated using commercially available techniques. The first prototype consists of a single slider and stator and generates a linear motion with a slider motion range of about 5 mm. It weighs 7 g and generates a power of 1.6 W and a thrust force of 4.4 N. The second prototype consists of a 50 layer stack of linear motors, summing their outputs. It weighs 3.6 kg and generates a propulsive force of 310 N being powered with boosted commercial three-phase electricity. The third prototype consists of a rotor and a stator in which electrodes are arranged radially and generate rotational motion. A maximum power of 3.6 mW was generated by the prototype weighing only 260 mg for its rotor and stator. From the results of the numerical calculation, a practical design methodology for the motor is determined. An optimal design for a motor employing currently available material and fabrication techniques is provided as an example. Analyses predict that force generation over the interfacial area between the slider and stator of this motor would be 3900 N/m/sup 2/.

Basic Design of Human-Symbiotic Robot EMIEW

We are developing a robot that supports people in their daily lives: a human-symbiotic robot. Such robot must share space with its users, be user-friendly, and be able to assist its users. We have developed a prototype autonomous mobile robot that makes use of a self-balancing two-wheeled mobile system and a body swing mechanism to shift its center of gravity. This allows it to move nimbly at up to 6 km per hour. It also has capabilities to avoid collisions with obstacles for moving safely through complex environments. Distant-speech-recognition and high-quality speech-synthesis technologies enable it to communicate with people naturally (i.e., without special tools). These capabilities were demonstrated at the 2005 World Exposition in Aichi, Japan

Power-assisted walking support system with imbalance compensation control for hemiplegics

Walking ability is essential for the elderly if they are to live a self-supported daily life. Conventional walkers have been used by people with weak lower limbs, but manipulating these walkers for desired direction is difficult for hemiplegic patients. This paper describes a power-assisted walking support system that allows these patients better control of their walk by compensating for the force input bias caused by their imbalanced gait. Experimental use by hemiplegics improved the stability and speed of their walk.

Gait Improvement by Power-Assisted Walking Support Device

This chapter presents the development and testing of a walker-type power-assisted walking support device for individuals who can hardly walk without help. This walker-type device assists the users gait by a power-assist control based on force input. Its dynamical characteristics can be easily adjusted by modifying the control parameters so that a wide range of users can use it. It can improve gaits of elderly people with various physical needs. The power-assisted walking support device has four wheels and a supporting pad that holds the user With this control system, the user can intuitively manipulate the walker at their own pace. The variable parameters include viscous resistances and virtual inertias in the forward, backward and rotational directions and the parameter given to the imbalance compensator, that is, the amount of the virtual shift of the force sensor. Results demonstrate that the variable dynamics capability of the power-assist system provides high adaptability to various needs of the users.

Collision-avoidance algorithm for human-symbiotic robot

A real-time collision-avoidance algorithm for human-symbiotic robots that are required to avoid multiple pedestrians was developed. An algorithm to predict the likelihood of a collision with obstacles was based on the relative velocities between a moving robot and multiple obstacles. An algorithm that can generate the optimum path sequence to a goal in real time was also developed. The collision-avoidance path is generated by repeating an operation to select two tangent paths that connect a via-point on a path to a collision circle of each obstacle that exists in the relative space. A robot-called EMIEW”-using these algorithms with a system for avoiding collisions with many obstacles moves at a speed of 0.8 m/s in a cluster of five people walking at 1.2 m/s. The repeat period for generating a new avoidance path is 0.5s, and the processing time for the developed algorithm in the each period is a maximum of 4 ms.

Dual excitation electrostatic stepping motor

Electrostatic motors have been believed to be weaker than electromagnetic motors which are typically used for mechatronic devices. However, electrostatic motors are preferable to electromagnetic ones for micromechanical applications since their force per volume ratios increase as their dimensions are reduced. It follows that a large output should be obtained if a large number of such small motors with high force per volume ratios are linked and their outputs are aggregated. This paper proposes an electrostatic drive technology which is applicable to such a large-output motor. The element motor, called the dual excitation electrostatic stepping motor, consists of a pair of plastic films, slider and stator. Both films have parallelly located electrodes embedded in them, and the slider moves along the surface of the stator when defined rectangular pulse voltages are applied to the electrodes both in the slider and the stator. The force generation characteristic of the electrostatic motor is calculated by the surface charge method. A prototype fabricated using flexible print board technology weighs 7 g and generates a thrust force of 1.9 N at an excitation of ± 1000 V.