Yoshikazu Matsuo

Loop-shaping characteristics of a human operator in a force reflective manual control system

Deals with loop-shaping characteristics of a human operator in a manual control system with a force reflective controlling device (controlling lever). The system consists of a dual loop. The inner loop is force based and the outer loop is visual based. In the inner loop, a hand motion control loop, the operator applies a force to the lever to bring its position close to a hand (or lever) position command. In the outer loop the operator generates the command from information of the visual sensation such as a target position. This paper focuses on the inner loop, that is the hand position control system, and investigates its structure and properties. As a result, loop-shaping characteristics of a human operator in the hand motion control system are discovered. The characteristics correspond to the crossover model, well-known operators characteristics in manual control systems based on visual sensation. Further, it is confirmed that the discovered characteristics of the operator are explainable by the structure of the proposed model.

Design of a controller for an autonomous distributed multi-actuator system using genetic methods

In this paper, an autonomous distributed system consisting of multiple actuators loop-connected into a wheel shape was considered. In order to simplify the controller design procedure, genetic programming and genetic algorithms were employed to directly search for optimal torque functions of this multiactuator system of which nonlinearity and multiplicity of actuators make it difficult to determine the optimal torque functions analytically. As multiple torque functions corresponding to actuators in different states need to be obtained, multiple GP processes which share the same fitness value were executed in parallel. Though it is believed that GP is well suited to difficult control problems where no exact solution is known, at the population size of 50, commonly used GP failed to obtain an acceptable solution for this system. Step by step experiments demonstrate how GP with small population size can be used to improve a predetermined solution by using the proposed concepts of partially hinted initial population and common-branch crossover operator. Separately, another GA search method which manipulates directly on the values of the torque tables was employed and the simulation and experimental results of both methods were compared.

On sensing and control methods for super-mechano colonies

As a sub-theme of the TITech COE/SMS research project, we began the Super-Mechano Colony (SMC) project at the end of last year, addressing a new stage of collective robotics. After a short review of the related study fields, the motivation and the objective of the SMC project is described. Then, the current study plan of the SMC project is presented briefly. Finally, some preliminary study results for this project is reported.

Estimation of lumbar load by 2D reconstruction of spine line using wearable sensor system

Anteflexion is essential for many physical activities ranging from carrying objects through snow shoveling to farm work. However, lumbago is a common cause of anteflexion, in which lumbar disks are under a heavy load due to changes in lumbar spine shape. With the aim to reduce lumbago risk, in this study we developed a motion sensor system that can estimate the shape, posture and load on the lumbar spine from measuring the lumbar in the lumbar region when the lumbar spine shape changes and the pelvis posture angle changes. We present a wearable version of this sensor system, and propose an estimation method of the lumbar shape using the pelvis posture angle and lumbar region skin curvature from this system. In addition, we measure the anteflexion using this system and study the change in load of the lumbar spine caused by changes in posture.

Wearable Sensor System for Lumbosacral Load Estimation by Considering the Effect of External Load

Anteflexion of the spine is a crucial motion in performing many tasks during work and daily life. It is particularly important in tasks such as providing care to others and carrying objects. To devise measures for preventing back pain, it is necessary to determine the postures associated with high risk of low back pain. Postures that increase lumbosacral load should be identified to reduce the risk of low back pain. In previous work, the relationship between posture and intervertebral loading was clarified, and the centers of gravity in the upper body and the waist shape were estimated. Moreover, individual differences were considered to improve the accuracy of the estimation. This method can estimate the lumbosacral load with sufficient accuracy. However, lumbosacral loading was examined in relation to posture and increases with external load. Therefore, the external load should be included in lumbosacral load estimation. In this study, we developed a back muscle exertion estimation method by using stiffness sensors to measure back muscle exertion, because the back muscle exertion changes with the external load. We conducted experiments in which participants wore the sensor system and the lumbosacral load was estimated from the external load. Estimation using the muscle stiffness sensors was better than previous estimation methods.