Analysis of Effect of Motion Path on Leg Muscle Load and Evaluation of Device to Support Leg Motion During Robot Operation by Reducing Muscle Load

Because the human arm and leg have a similar skeletal structure, it may be possible to use the leg to operate a robot by the master-slave method. However, operation by the leg with six degrees of freedom has two problems. First, people move their ankle with a curved motion despite intending to move it linearly. Second, it is a burden for the operator to suspend their legs in the air during operation. This study dealt with these problems. For the first problem, we hypothesized that one of the reasons was that the muscle load of a curved motion was smaller than that of a linear motion, and we quantitatively compared them by musculoskeletal analysis. The muscle loads of curved motions were 20% smaller in the anteroposterior direction, 3.1% to 23.8% smaller in the lateral direction, and 10% smaller in the vertical direction than linear motions, which showed that the hypothesis was consistent. Further, comparison of the analysis results with the results of a previous study suggested that subjects unconsciously tried to reduce the muscle load and to move closer to a linear line when they moved their ankle while consciously intending to make a linear motion. For the second problem, we developed two different prototypes of a leg support device. An experiment to evaluate the effectiveness of these devices showed that subjective exercise intensity of the tasks in the experiment using the devices was 40% or more less than that without the device, which proved the effectiveness of the devices

Posture Operating Method by Foot Posture Change and Characteristics of Foot Motion

The lower limbs of the human body actually can perform the multiple-degree-of-freedom motion, just like the upper limbs. This suggests the possibility for the lower limbs to be used in the operation of multiple-degree-of-freedom devices, such as a robot arm. With that point in mind, the present paper focuses on the foot motion and examines its characteristics under the situation in which the posture of the object is manipulated by the posture change of the foot. First, we investigated how well the foot of the operator moved in accordance with the intention of the operator in order to clarify the motion characteristics of the foot experimentally by measuring the foot motion with a motion capture system under the assumption that the operator manipulates an object in virtual space. The results showed that there are differences between the intended and actual foot motions, especially when the tilt angle change was accompanied by a rotation angle change, which might be because of the joints whose axes of motion are nonparallel to the foot coordinate system, such as the talocalcaneal joint or Chopart joint. Next, an operating system considering the motion characteristics of the foot was proposed, and an experiment to verify its effectiveness was conducted. When the proposed conversion formula was used to calculate the intended foot motion based on the actual foot motion, the operability improved with respect to the required time and path-following accuracy while manipulating an object to the target posture and with respect to subjective operability

Effect of Viewpoint Change on Robot Hand Operation by Gesture-and Button-Based Methods

Teaching pendants with multiple buttons are com-monly employed to control working robots; however, such devices are not easy to operate. As an alternative, gesture-based manipulation methods using the oper-ator’s upper limb movements have been studied as a way to operate the robots intuitively. Previous studies involving these methods have generally failed to con-sider the changing viewpoint of the operator relative to the robot, which may adversely affect operability. This study proposes a novel evaluation method and applies it in a series of experiments to compare the influence of viewpoint change on the operability of the gesture-and button-based operation methods. Experimental results indicate that the operability of the gesture-based method is superior to that of the button-based method for all viewpoint angles, due mainly to shorter non-operating times. An investigation of trial-and-error operation indicates that viewpoint change makes po-sitional operation with the button-based method more difficult but has a relatively minor influence on postu-ral operation