Power Assist System Operable from Arbitrary Operational Point Considering on Human Cognition and Motor Function

The practical power assist systems (PAS) such as material handling equipments represented bybalancers are utilized widely in heavy weight transportation in factories or warehouses now.These manipulators composing a PAS have large workspace. However, most PAS has an inputinterface near the end-effecter of the manipulator, actual workspace is limited by user's motion space. As a result, the users have to be close to the end-effecter and it has a risk for example falling accident. As a solution of that, using control stick or master-slave system are general.However, these solutions require to acquaint how to use each control method. Furthermore, toapply maneuverability to improve method such as force feedback is required expensive costs.In this study, the goals are not only amplifying the operational force, but also extendingthe workspace and keeping intuitive maneuverability. Concretely, Multi-portal Human Interface(M-HI) as an innovative human interface for power assist systems has been researched anddeveloped. The M-HI allows users to apply the operational force anywhere on the power assistsystem. Because of that, the workspace of the power assist system is extended with their end-effecter can be controlled as user think.Previous research shows that controlling end-effecter from each intermediate joint of PAS isable. However, it is confirmed that the maneuverability decrease in that situation. Many kinds of things are thinkable as the causes of that phenomenon. In this study, maneuverability improves method focused on human characteristics and human-machine system are proposed.When the user operates PAS, the user confirms end-effecter and target object by them eyes.It is reported that human motion are affected by their visual information. However, the effect to PAS maneuverability caused by user's visuospatial recognition has not been reported. The relation between user's operational force and user's line of sight are analyzed in terms of human vision. The operational force stabilization methods are proposed considering these relationships.In this study, impedance control of PAS's end-effecter is adopted as a fundamental control method. While the PAS is controlled with M-HI, motions of end-effecter and operational pointare different each other. Because of that, the impedance parameters of operational point aredifferent from desired values on end-effecter position. This phenomenon decreases the maneu-verability of the PAS with M-HI. The relationship between maneuverability and the impedance parameter difference of operational point is confirmed experimentally. Furthermore, the modification method to make the impedance parameters closer to desired values is proposed. The proposed method improves the maneuverability of the PAS with M-HI. The difference of themotions of end-effecter and operational point also cause the interference force between the userand PAS on the operational point. The effect of the interference force to the maneuverabilityof the PAS are confirmed. The the interference force reduction method is proposed and themaneuverability improves effect are examined by simulation and experiment.