This paper proposes a high-safety power-assisted cart that can be operated on a slope by applying little-changed manual power even if the inclination changes. In this cart, balancing operation to compensate for load increments due to the increase in the inclination by using a spring is achieved in the safe state with the cart held by the brake application, while dangerous moving operation is performed by safe human power. Firstly, this paper describes a passive dynamic control and an inherently safe control, both of which form the basis of the system of the power-assisted cart, and the principle of a power assist system using a coil spring. Secondly, this paper describes the mechanism and control sequence of the power-assisted cart. Lastly, this paper verifies the effectiveness of the power-assisted cart by experiments.

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.

The passive dynamic control (“PDC”) is a mechanical system control method based on an inherently safe design. It positively uses a brake having variable characteristics. In this paper, the PDC is applied to a two-link pneumatic artificial muscle manipulator. First, new mechanism in which two arms are controlled separately is proposed, and its control method based on operation of MR brakes is described. Then, the effectiveness of the proposed control method is examined through experiments of positioning control and circular follow-up control.

The passive dynamic control ("PDC") is a new mechanical system control method using variable passive elements with less energy and more safety. In the study described in this paper, the PDC is applied to a pneumatic cylinder for positioning control. When an object is stopped in the intermediate position by a pneumatic control and an electromagnetic friction brake, the unbalance force is cut to zero and the balanced state is achieved. Thus, high-rigidity positioning is achieved and the object can be moved to the next position. In this paper, the authors also propose a method of improving the internal pressure control precision for the cylinder.

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

In this paper, we discuss a method to achieve safe autonomous robot system coexistence (or Kyozon in Japanese). First, we clarify human pain tolerance and point out that a robot working next to an operator should be covered with a soft material. Thus, we propose a concept and a design method of covering a robot with a viscoelastic material to achieve both impact force attenuation and contact sensitivity, keeping within the human pain tolerance limit. We stress the necessity of a simple robot system from the viewpoint of reliability. We provide a method of sensing contact force without any force sensors by monitoring the direct drive motor current and velocity of the robot. Finally, we covered a two-link arm manipulator with the optimum soft covering material, and applied the developed manipulator system to practical coexistence tasks.