Daisuke Gunji

Grasping force control of multi-fingered robot hand based on slip detection using tactile sensor

To achieve a human like grasping with a multi- fingered robot hand, the grasping force should be controlled without using information from the grasped object such as its weight and friction coefficient. In this study, we propose a method for detecting the slip of a grasped object using the force output of Center of Pressure (CoP) tactile sensors. CoP sensors can measure the center position of a distributed load and the total load applied on the surface of the sensor, within 1 ms. These sensors are arranged on the fingers of the robot hand, and their effectiveness as slip detecting sensors is confirmed in tests of slip detection during grasping. Finally, we propose a method for controlling grasping force to resist tangential force applied to the grasped object using a feedback control system with the CoP sensor force output.

Development of Wireless In-Wheel Motor Using Magnetic Resonance Coupling

In-wheel motors (IWMs) in electric vehicles are particularly important for motion control. A conventional IWM is powered from a battery aboard the vehicle via cables. Since power cables and signal cables of an IWM are exposed to harsh environments, they can possibly become disconnected by high acceleration or vibration. In order to overcome this problem, the wireless-in wheel motor (W-IWM) has been proposed. The risk of disconnection would disappear if the cables of the IWM are removed. One way to implement wireless power transfer is by utilizing the magnetic resonance coupling method. However, motion of the W-IWM, and thus, a misalignment between the wheel and the vehicle, leads to variations in the secondary-side voltage provided. To account for this, this paper discusses two new control methods. One proposed method maintains the secondary voltage using a hysteresis comparator. The other proposed method estimates the secondary inverter output power, applying it to a feedforward controller in order to keep the secondary dc-link voltage constant. Experimental results show that these methods can drive a W-IWM effectively with high efficiency.

Fundamental research of power conversion circuit control for wireless In-Wheel Motor using magnetic resonance coupling

The In-Wheel Motor (IWM) is the most preferable driving mechanism of electric vehicles for vehicle motion control, energy efficiency, and vehicle design flexibility. One technical issue of the IWM is the reliability of power and signal wires. Wireless power transfer technology is the best solution. In this paper, a bidirectional wireless power transfer circuit using a primary inverter and a secondary converter is proposed. We propose a control method of both the inverter and the converter to stabilize the secondary DC-link voltage. The proposed method is verified by simulation and experiments using simulated test equipment.

Basic study of transmitting power control method without signal communication for Wireless In-Wheel Motor via magnetic resonance coupling

In order to improve reliability and safety of an In-Wheel Motor, the Wireless In-Wheel Motor (W-IWM) using magnetic resonance coupling has been proposed. Transmitting power of the W-IWM is controlled by the primary inverter and the secondary converter. One of a technical issue of the W-IWM is transmitting power variation due to the load power variation and the coupling coefficient variation. In this paper, we propose feedback control method of the transmitting power on the primary side using primary voltage margin. The primary voltage margin can be measured by the primary current. The proposed method requires no signal communication between the primary side and the secondary side. The effectiveness of the proposed method is verified by simulation and experiment.

Efficiency analysis of powertrain with toroidal continuously variable transmission for Electric Vehicles

In order to extend electric mileage per charge of Electric Vehicles (EVs), the powertrain efficiency should be further improved. A possible solution is employing transmission which is properly optimized for EV. Continuously variable transmission (CVT) is especially suitable, because it maintains the operating condition of electric motor being closer to the most efficient region even while vehicle speed is changing. In this paper, a toroidal CVT and a single ratio transmission are compared by numerical simulations regarding the overall efficiency. Toroidal CVT has an advantage for high torque-low speed region and low torque-high speed region. However, regarding the rest, the efficiency degrades in contrast. In order to improve the overall efficiency, the best implementation approach is introduced.

Stability analysis of constant power load and load voltage control method for Wireless In-Wheel Motor

In order to improve motion control performance of electric vehicles (EVs), In-Wheel Motor (IWM) is the most preferred electric motor arrangement. Our research group has proposed Wireless In-Wheel Motor (W-IWM) concept to solve some technical problems of an IWM, which are reliability and safety issues of power and signal wires. In this research, we did a stability analysis of Series-Series compensated wireless power transfer via magnetic resonance coupling with constant power load. Analysis result is verified by circuit simulation. Also, we propose a load voltage control method using a secondary converter. The effectiveness of the proposed control method has been verified by simulation and experiment using small power test equipment.

Grasping force control of multi-fingered robot hand based on slip detection sing tactile sensor

To achieve a human like grasping with a multi-fingered robot hand, the grasping force should be controlled without using information from the grasped object such as its weight and friction coefficient. In this study, we propose a method for detecting the slip of a grasped object using the force output of center of pressure (CoP) tactile sensors. CoP sensors can measure the center position of a distributed load and the total load applied on the surface of the sensor, within 1 ms. These sensors are arranged on the fingers of the robot hand, and their effectiveness as slip detecting sensors is confirmed in tests of slip detection during grasping. Finally, we propose a method for controlling grasping force to resist tangential force applied to the grasped object using a feedback control system with the CoP sensor force output.

Operating point setting method for wireless power transfer with constant voltage load

Wireless Power Transfer (WPT) has been widely researched in many application fields. Typical application to vehicle field is wireless charging for electric vehicles while parking and driving. Some power conversion circuit structures and its control method have been proposed in previous researches, for example, transmitting power control and efficiency maximizing control using a secondary-side DC-DC converter. However, selection method of optimal circuit structure for desired control is not clear. In this research, we propose generalized power conversion circuit structure on Series-Series compensated WPT circuit. Load current and power transfer efficiency are analyzed using equivalent AC resistance model about WPT circuit with constant voltage load. Then, we formulate operation points for desired control with consideration for operating condition.

Slip ratio control using load-side high-resolution encoder for in-wheel-motor with reduction gear

Electric vehicles have recently attracted broad attention. Advantage of Electric Vehicles is not only environmental performance but also higher response vehicle motion control when compared to internal combustion engine vehicle. In order to improve motion control performance of Electric Vehicles, applying high-resolution encoders both on a motor side and a wheel side is a good solution. In this paper, the design of the actual vehicle unit for experimental electric vehicle FPEV4-Sawyer is explained. Furthermore, the effectiveness of using high-resolution encoder on vehicle motion control methods is discussed with simulations and experiments of slip ratio control.