This paper proposes a modeling method for the haptic information from the environmental characteristics of a plane. A human obtains much haptic information by touching an object. For the haptic information derived from a rubbing motion, this paper particularly focuses on the vibration components of the friction force. Although there are many methods to describe the friction force, it is difficult to treat them quantitatively. This paper proposes applying Cepstral analysis to haptic information to easily extract and treat unique features of the environment. A technique for representing the extracted frequency features is also presented. An experiment was performed using a 2 DOF system to show the validity of the proposal.
This paper proposes a new force control based on a bilateral control structure. Improvements in motion control technology, including force control, are important to realizing a human support robotic system. Conventionally, robot systems require high-precision positioning accuracy. In the near future, however, robots will need to be involved in human society directly. In this case, force control with high precision is an essential part of robot system control. For a complex system, raising the controller gain and bandwidth is not easy. In the proposed system, a virtual position control loop is constructed in a conventional force control to assist with ideal acceleration control. With the proposed system, high-accuracy force control and a control band can be achieved with superior performance compared to conventional systems.
Landing radar that measures the velocity and the altitude of the airframe has been developed for the sensor, which helps safe landing. In applications where the observation range is limited to a very short range such as the final stage of landing, we can expect to obtain a high signal-to-noise (S/N) ratio. In these situations, the multiple frequency continuous wave (CW) with MUSIC (MUltiple SIgnal Classification) algorithm is considered to be useful for achieving a high resolution with a low sampling rate of several tens of kilohertz and relatively low-speed signal processing. In this paper, the multiple frequency CW with 1D and 2D MUSIC algorithm to measure the altitude is described. The simulation shows that the bias errors in both methods are less than 1% of the altitudes. The random errors of 1D MUSIC and 2D MUSIC are 1.3%-1.7% and 0.8%-1.0%, respectively. The random errors of 2D MUSIC are smaller than those of 1D MUSIC. We also show the fundamental experimental results obtained in an athletic field using the radar fitted on a cage lifted by a crane. We could obtain stable estimation results on altitudes between 1.0m and 7.0m. These results indicate that the multiple frequency CW radar is one of the effective tools for landing radar in the final phase of landing.
Nanoscale motion control is required for the miniaturization and performance improvement of mechatronic systems. In motion control at the nanometer scale, disturbances that do not affect the system at the macro scale might greatly influence the control performance. The torque ripple caused by current distortion is one of the most serious disturbance elements and should be eliminated. Compensation methods for current distortion have been researched, but the conventional method cannot be applied to control systems in the nanometer scale because a short sampling time is needed. To address this problem, a filter design method is proposed in this paper. The effect of the current distortion can be reduced by designing the filter in the disturbance observer to have a low-pass filter and a band-stop filter. By using high-precision acceleration control based on the proposed method, persistent oscillation can be suppressed, and control accuracy can be improved. The validity of the proposal is comfirmed by experiments.
Multilevel converters have a number of capacitors as sources of multilevel voltages. The volume of the capacitors should be minimized to realize a high-power-density converter. In this paper, the selection criteria of the capacitors in a flying capacitor converter are investigated. In this type of converter, the required capacitance, consequently, volume of the capacitors are decreased when the PWM carrier frequency is higher. However, there is a limitation on the reduction in the volume due to the temperature increase caused by the power losses in the capacitors when the volume becomes small during high-PWM-frequency operation. On the basis of an investigation including the temperature increase, it is clarified that a capacitor with a high capacitance density is not necessarily the best for the flying capacitor depending on the operating conditions.