Falling is a serious problem with the growing elderly population. In this sense, clinical institutions have implemented motor function assessment programs. In particular, the timed up and go test (TUG) is the most frequently applied clinical trial to assess the elderly walking ability in many clinical institutions and communities. In this study, we proposed a gait measurement system that can evaluate motor function in dynamic gait tests, such as the TUG test, using the point clouds of depth sensors (Kinect). The TUG test is a dynamic task that includes 3m of walking and turning motion. However, estimating joint positions using conventional methods that use Kinect skeleton function or point clouds is difficult. To solve these problems, before applying the iterative closest point algorithm, we proposed a method to move the segment model to a pre-estimated position and perform matching. In the accuracy verification experiments of several young people, the average error of each joint position was less than approximately 0.03 m, and the average error of the knee angle was approximately 4.54 to 5.13 degrees. These results indicate that the values estimated by the proposed method are useful as values for evaluating clinical tasks.
One of the most basic tasks that a dual-arm robot does is pick-up and place work. Pick-up and place work consists of tasks in which the robot carries objects from a start position (initial position) to a goal position. The following three important points should also be considered when the dual-arm robot does this work efficiently: 1) collision avoidance of the arms, 2) which arm should move an object, and 3) the order in which the objects should be picked up and placed. In addition, dual-arm robot has operation range constraints. Depending on the position relationship between a start position and goal position, unless both arms are used, the object may not be transferred to a goal position. In this paper, we define the transfer path which must use both arms as "shared transfer path". Therefore, we propose a motion planning method to achieve efficient pick-up and place work considering shred transfer path. First, we use mixed integer linear programming (MILP) based planning for the pick-up and place work to determine which arm should move an object and in which order these objects should be moved while considering the dual-arm robot's operation range. Second, we plan the path using the rapidly exploring random tree (RRT) so that the arms do not collide, enabling the robot to perform efficient pick-up and place work based on the MILP planning solution. The effectiveness of proposed method is confirmed by simulations and experiments using the HIRO dual-arm robot.
For a companion robot that follows a person as an assistant, predicting human walking is important to produce a proactive movement that is helpful to maintain an appropriate area decided by the human personal space. However, fully trusting the prediction may result in obstructing human walking because it is not always accurate. Hence, we consider the estimation of uncertainty (i.e., entropy) of the prediction to enable the robot to move without causing overconfident motion and without being late for the person it follows. To consider this uncertainty of the prediction to the controller, we introduce a reliability value that changes based on the entropy of the prediction. This value expresses the extent the controller should trust the prediction result, and it affects the cost function of our controller. We propose an uncertainty-aware robot controller based on nonlinear model predictive control to realize natural human-followings. We found that our uncertainty-aware control system can produce an appropriate robot movement, such as not obstructing the human walking and avoiding delay, in both simulations using actual human walking data and real-robot experiments.
A vibration-isolating bed for ambulances using an inerter is proposed. The structure of the vibration-isolating bed is assumed to consist of a bottom frame fixed to the ambulance floor and an upper frame on which the stretcher is placed. Both are connected only by the suspension, including the inerter, in the vertical and horizontal directions. Because the inerter can reduce the gain of the high frequency band and delay the response, the time when maximum acceleration is applied to vibration-isolating bed can be shortened in a limited space in ambulance. We consider the vibration-isolating bed as a plant and the designed suspension as a controller, and then formulate the state equation. To reduce the acceleration within the movable range of the bed in ambulance, the controller that minimizes the H∞ norm of the transfer function from the external force acting on the vibration-isolating bed to vibration-isolating bed acceleration is calculated by bilinear matrix inequality. The transfer function determinates the structure and coefficient of the suspension by assuming that the transfer function is the sum of mechanical admittance of spring, damper and inerter. The usefulness of the vibration-isolating bed is verified by numerical simulations by using MATLAB assuming braking and turning.
The early phase of design contains uncertain design information. Therefore, the boundary condition of a design problem often change as the design process progresses because of the change and addition of required performance or other constrained condition. Designers need to modify design solutions to accommodate design changes using iterative process until required performances are satisfied. Designers spend many times on design changes in progress at conventional design method because designers try to define design variables as point values up to satisfying required performances several times. In contrast to the conventional design method, set-based design method represents design variables as not point values but ranged values and obtains design solution sets with ranged values. This paper proposes a new design method. That defines design variables as ranged values, obtains diverse design solution sets. The possible distributions from design variables are calculated using PSO to accommodate the boundary condition change and presents designers obtained diverse design solution sets and their possible distributions using GUI. This paper applies the proposed design method to the design problem of the isolation system for vertical earthquake vibration and shows the effectiveness of this study for accommodating the boundary condition change.
