Toshiki Moriguchi

Developing a mobile robot for transport applications in the hospital domain

We have been developing MKR (Muratec Keio Robot), an autonomous omni-directional mobile transfer robot system for hospital applications. This robot has a wagon truck to transfer luggage, important specimens, and other materials. This study proposes an obstacle collision avoidance technique for the wagon truck pulling robot which uses an omni-directional wheel system as a safe movement technology. Moreover, this paper proposes a method to reach the goal along a global path computed by path planning without colliding with static and dynamic obstacles. The method is based on virtual potential fields. Several modules with different prediction times are processed in parallel to change the robot response according to its relative velocity and position with respect to the obstacles. The virtual force calculated from each potential field is used to generate the velocity command. Some experiments were carried out to verify the performance of the proposed method. From the experimental results in a hospital it was confirmed that the robot can move along its global path, and reach the goal without colliding with static and moving obstacles.

Development of measurement system for task oriented step tracking using laser range finder.

BackgroundAvoiding a fall requires fast and appropriate step responses, stepping speed as a fall risk indicator has only been assessed in older adults. We have developed a new measurement system that applies a laser range finder to assess temporal and spatial parameters of stepping performance such as step speed, length, and accuracy. This measurement system has higher portability, lower cost, and can analyze a larger number of temporal and spatial parameters than existing measurement systems. The aim of this study was to quantify the system for measuring reaction time and stride duration by compared to that obtained using a force platform.MethodsTen healthy young adults performed steps in response to visual cues. The measurement system applied a laser range finder to measure the position and velocity of the center of each leg and of both legs.We applied the developed measurement system to the rhythmic stepping exercise and measured reaction time and stride duration. In addition, the foot-off time and foot-contact time were quantified using the measurement system, and compared to the foot-off time and foot-contact time quantified using a force platform.ResultsWe confirmed that the measurement system can detect where a participant stood and measured reaction time and stride duration.Remarkable consistency was observed in the test-retest reliability of the foot-off time and foot-contact time quantified by the measurement system (p < 0.001). The foot-off time and foot-contact time quantified by the measurement system were highly correlated with the foot-off time and foot-contact time quantified by the force platform (reaction time: r = 0.997, stride duration: r = 0.879; p < 0.001).ConclusionsThe new measurement system provided a valid measure of temporal step parameters in young healthy adults.The validity of the system to measure reaction time and stride duration was evaluated, and confirmed by applying to the rhythmic stepping exercise.

Improved Leg Tracking Considering Gait Phase and Spline-Based Interpolation during Turning Motion in Walk Tests.

Falling is a common problem in the growing elderly population, and fall-risk assessment systems are needed for community-based fall prevention programs. In particular, the timed up and go test (TUG) is the clinical test most often used to evaluate elderly individual ambulatory ability in many clinical institutions or local communities. This study presents an improved leg tracking method using a laser range sensor (LRS) for a gait measurement system to evaluate the motor function in walk tests, such as the TUG. The system tracks both legs and measures the trajectory of both legs. However, both legs might be close to each other, and one leg might be hidden from the sensor. This is especially the case during the turning motion in the TUG, where the time that a leg is hidden from the LRS is longer than that during straight walking and the moving direction rapidly changes. These situations are likely to lead to false tracking and deteriorate the measurement accuracy of the leg positions. To solve these problems, a novel data association considering gait phase and a Catmull–Rom spline-based interpolation during the occlusion are proposed. From the experimental results with young people, we confirm that the proposed methods can reduce the chances of false tracking. In addition, we verify the measurement accuracy of the leg trajectory compared to a three-dimensional motion analysis system (VICON).

Gait measurement system for the multi-target stepping task using a laser range sensor.

For the prevention of falling in the elderly, gait training has been proposed using tasks such as the multi-target stepping task (MTST), in which participants step on assigned colored targets. This study presents a gait measurement system using a laser range sensor for the MTST to evaluate the risk of falling. The system tracks both legs and measures general walking parameters such as stride length and walking speed. Additionally, it judges whether the participant steps on the assigned colored targets and detects cross steps to evaluate cognitive function. However, situations in which one leg is hidden from the sensor or the legs are close occur and are likely to lead to losing track of the legs or false tracking. To solve these problems, we propose a novel leg detection method with five observed leg patterns and global nearest neighbor-based data association with a variable validation region based on the state of each leg. In addition, methods to judge target steps and detect cross steps based on leg trajectory are proposed. From the experimental results with the elderly, it is confirmed that the proposed system can improve leg-tracking performance, judge target steps and detect cross steps with high accuracy.

Improved leg tracking with data association considering gait phase during turning motion in walk tests

Falling is a common problem in the growing elderly population and fall-risk assessment systems are needed for community-based fall prevention programs. In particular, the timed up & go test (TUG) is the clinical test most often used to evaluate elderly individual ambulatory ability in many clinical institutions or local communities. This paper presents an improved leg tracking method using a laser range sensor (LRS) for a gait measurement system to evaluate the motor function in walk tests such as TUG. The system tracks both legs and measures the trajectory of both legs. However, both legs might be close to each other and one leg might be hidden from the sensor. This is especially the case during the turning motion in the TUG, where the time that a leg is hidden from the LRS is longer than that during straight walking and the moving direction rapidly changes. These situations are likely to lead to false tracking and deteriorate the measurement accuracy of the leg positions. To solve these problems, a novel data association method considering the gait phase is proposed. From the experimental results with young people, we confirm that the proposed methods can reduce the chances of false tracking. In addition, we verify the measurement accuracy of the leg trajectory compared with a three-dimensional motion analysis system (VICON).

Development of measurement system for task oriented step tracking using laser range finder

Avoiding falls require fast and appropriate step responses, which has been assessed by only stepping speed as an indicator of fall risk in older adults. We develop a new measurement system that applies a laser range finder for convenient assessment of stepping performance including temporal and spatial parameters such as reaction time, step velocity, step length, and accuracy. The measurement system for step tracking has a large advantage in terms of portability, cost, and the number of temporal and spatial parameters that we can measure. The aim of this study is to verify an efficacy of the measurement system for step tracking. We developed the system that applied a laser range finder for convenient assessment of stepping performance. In the test using a force platform and the developed measurement system simultaneously, based on reliability and validity, its effectiveness is confirmed.Copyright