A prototype phase-detection ranging system based on the automotive remote/tele-control narrowband ARIB STDT108 standard and operating in the sub-GHz band is designed, built, and evaluated. The prototype uses a pair of transceivers operating asynchronously. Problems with the frequency offset and initial phase are overcome by using an exchange sequence. The prototype employing 5.6MHz bandwidth achieves a distance error of 0.09 m under ideal environments without multipath and 0.88 m in outdoor conditions within the range of 6.0 m × 6.0 m area.

In this paper, we propose a cooperative control of a wearable robot for paraplegics. The control system adjusts the stride length and walking velocity of a robot according to user's voluntary movement while generating a continuous walking pattern. We assume that the desired stride length and walking speed correspond to the preceding motion of a walking aid (walker), and the motion of the walker by the user was measured by a laser range sensor and an accelerometer. The continuous walking pattern during a step was planned by optimization of joint trajectories under inequality conditions. To perform continuous walking, the desired trajectory is required before the walker movement. To adjust the foot placement according to the walker movement, the desired walking pattern in the late swing phase is replanned. For the latest movement distance of the walker, the posture at heel strike is modified by Newton-like iterative calculations. We confirmed that a normal subject could walk continuously with a wearable robot controlled by our system while changing the stride length and walking speed.

In this paper, we propose an alternative motion planning method for a wearable robot with a variable stride length and walking speed. Trajectories are planned in a joint space rather than a workspace to avoid an ill-posed problem with no solution in inverse kinematics, and to consider the joint's range of motion, maximum velocity, foot clearance, and backward balance. The joint trajectories are represented by minimum jerk trajectories. Two via-points are assigned, and the parameters (angle and angular velocity) at the via-points are determined by applying an inverted pendulum model or optimization to satisfy the constraints. The fastest gait pattern generated by the proposed algorithm was twice as fast as the pattern generated by the workspace-based planning method. We confirmed that the fastest walking pattern of 0.36 m/s was feasible on a treadmill, and a walking pattern of 0.27 m/s was found for walking across the floor with a walker. Furthermore, the proposed method required approximately 65% of the electric power for the workspace-based method for the same walking speed and stride length. These results suggest that the proposed motion planning method is effective at generating a high-speed and efficient gait pattern for a wearable robot.

A software defined radio with the analog stage using the direct conversion principle and the digital stage using a DSP demodulator has been developed. The developed receiver realizes a multi-band characteristic of the 1.5 GHz and 1.9 GHz bands and a broadband characteristic up to 10 MHz together with a demodulation function of /spl pi//4-QPSK and GMSK, and the overall receiver performance was confirmed.