Takanori Kiyota

Inherently Safe Design of Home Elevator System by Passive Dynamic Control

The passive dynamic control (“PDC”) is a new mechanical system control method requiring less energy but ensuring higher safety, which is based on inherently safe design using variable passive elements. The PDC divides its control process into four steps: hold step, take-over step, unbalance step and free step. In each of these steps, it is confirmed that the next step has satisfied the inherently safe design and then the execution of the next step is permitted. In this study, the authors have developed a PDC balancer equipped with a constant-load spring balancer to provide a constant tension regardless of the wire elongation, and conducted positioning experiments using this PDC balancer. This paper proposes a new home elevator system using the PDC balancer. When the balance of the elevator is maintained by using the PDC balancer, the elevator can be moved by a small force. Even if power failure occurs or severance is caused to the spring of the PDC balancer, as long as the cage of the elevator is so mechanically arranged as to ascend in such case, impact on the passengers will be mitigated to be smaller than impact when it descends. Furthermore, this elevator is so designed as to prevent the passengers from being confined in the cage. The inherently safe design can be realized by multiplying the spring structure and employing the PDC for this system. This system is featured by its excellence in safety, energy saving and cost performance. If this system is realized, the home elevator can be used even in remote areas, which is expected to facilitate the spread of the home elevator.© 2007 ASME

Follow-up control of pneumatic cylinders by passive dynamic control

The passive dynamic control (ldquoPDCrdquo) is a new mechanical system control method based on inherently safe design, having energy-saving effect and high safety. The authors made an experimental setup (PDC pneumatic cylinder), pneumatic cylinders equipped with an electromagnetic friction brake and a load cell, respectively, and demonstrated the effectiveness of the PDC-applied positioning control. This paper describes two types of follow-up controls using such PDC pneumatic cylinder: one is trajectory follow-up control to follow up a circular trajectory biaxially, and the other is time follow-up control to follow up a sine curve uniaxially.

3D-free rescue robot system

This paper introduces a 3D-free rescue robot system which mainly consists of a moving vehicle with automatic outriggers, a 3D reaching arm and a spring balancer. This robot system lightens the weight of firemen at rescue activities on this system, supports his/her rescue activities by widening his/her working area, and reduces various risks entailing for the activities. The spring balancer is added with new functions for improvement, including high-performance passive dynamic control (PDC). Furthermore, the safety of this robot system is examined especially on fail-safe interlock

Development of constant torque device and its application to power assist systems

Various power assist systems are used in the fields of manufacturing and welfare. Those power assist systems that handle a heavy object directly by the manual actuating force often use a force sensor to detect the moving direction. However, the force sensor has problems, including one that it is susceptible to noise. In the circumstances, this paper proposes a motor-driven device for supplying constant torque and its application to direct-handling type power assist systems. First, this paper overviews a passive dynamic control (PDC), on which this system is based. Second, this paper shows the principle of detecting the direction of movement not by using force but by using the displacement from the balancing state realized by spring action, which is assumed as the basic state. Third, this paper describes the development of the constant torque device based on this principle of detection, and demonstrates its effectiveness as a power assist system by basic experiments. Since this system may satisfy the fail-safe conditions, it is expected to be used as a high-safety device to make up for the deficits of DD motors.

Direct-handling enabled power assist system using coil spring

Various types of power assist systems are desired in the fields of manufacturing, farming, welfare, etc. In the direct handling which applies force directly to a heavy object, operating force is usually detected by using a force sensor. However, the force sensor is deficient in that, for example, it is sensitive to noise. In this paper, the authors propose a direct-handling enabled power assist system for handling heavy objects in the vertical direction. The system converts the operating force into the angular displacement using a coil spring as a passive element, and detects the direction of the converted force by using a displacement sensor. Any system which coexists and operates with humans is required to ensure high safety. In view of this, the authors will verify the operability of the proposed system, and demonstrate that the system has higher safety in comparison with the systems using a force sensor.

Enclosing control based on brake operation and its application to pneumatic systems

The passive dynamic control (“PDC”) is a mechanical system control method based on an inherently safe design positively using the braking force. This paper proposes enclosing control in which deviation from a target trajectory is controlled by a brake mechanism. First, the principle of the enclosing control is described. Second, an experimental setup using two PDC pneumatic cylinders equipped with an electromagnetic friction brake and a load cell is described. Third, the effectiveness of the enclosing control is verified in an experiment of follow-up control for a circular trajectory and comparison with PI control. Last, the enclosing control is applied to follow-up control for an arbitrary trajectory.

Trajectory follow-up control by enclosing control with rotary pneumatic 2-link manipulator

The passive dynamic control (PDC) is a mechanical system control method based on an inherently safe design means using a brake mechanism effectively. Since control only with an actuator does not have a stopping mechanism, this kind of control cannot prevent deviation from the target trajectory in case of trouble. On the other hand, the PDC follow-up control can prevent deviation from the target trajectory by operating the brake mechanism. Since the PDC follow-up control can be envisaged as gradually narrowing down the wide area around a control object to enclose it toward the target trajectory, the authors designate this control as “enclosing control.” This paper describes the application of the enclosing control to a rotary pneumatic manipulator. First, in a sine track trajectory follow-up control experiment using only one link, the effectiveness of the PDC is demonstrated in comparison with the PI control. Next, in a circular trajectory follow-up control experiment using a 2-link manipulator, the effect of the enclosing control is verified.