Naoki Motoi

Task Realization by a Force-Based Variable Compliance Controller for Flexible Motion Control Systems

This paper proposes a task realization method by using a force-based variable compliance controller for flexible motion control systems. In recent years, the robots working in human life space are desirable. Considering the robots working in human life space, they should achieve the safety motion. From this viewpoint, one of the key technologies is flexible motion control system. Of course, task realization instead of human beings is important. Therefore, it is necessary to propose the realization method of several tasks for the flexible motion control systems. In this paper, two robot tasks are defined: “approach task” and “pushing task.” The approach task is the motion for a robot to approach an environment and not to contact the environment. On the other hand, the pushing task is the motion for the robot to contact and push the environment in order to achieve the several tasks. For the realization of the several tasks to the environment, it is necessary to achieve both the position control during the approach task and the force control during the pushing task. Therefore, the controller has to be modified depending on the contact state, which means whether the robot is in contact with the environment or not. In order to modify the controller, the variable compliance gain which is varied according to the contact state is proposed. Focusing on the approach task, the position control which is equivalent to the conventional position-based compliance method is achieved by using the proposed method. On the other hand, the proposed controller is suitable for the pushing task compared with the conventional position-based compliance controller since the proposed controller is based on the force control. Therefore, several tasks which include the position tracking and the contact with the environment are actualized by using the proposed method. In addition, the performance analysis by a Bode diagram and stability analysis by root loci are conducted. The validity of the proposed method is confirmed from the experimental results.

Transient behavior of the dual active bridge converter in high efficient energy conversion system

This paper shows the transient behavior of a system which boosts a part of the battery voltage for a electric vehicle. This system consists of the powertrain of electric vehicles and a bi-directional isolated DC-DC converter called dual active bridge (DAB). This system can compensate the battery voltage drops with high efficiency compared with the conventional series chopper system. In many studies, the DAB converter operates in the steady state. On the other hand, this paper analyzes the operation of the DAB converter in the transient state. Especially, the operation at the start of the DAB converter is focused on.

A prediction method considering object motion for humanoid robot with visual sensor

This paper proposes a prediction method considering object motion for a humanoid robot with a visual sensor. A visual servo control method is one of the useful methods to control the robot based on visual information. Robot can track the movable object by using this method. However, this system does not consider the future response of the object motion. As a result, the delay arises. In order to solve this problem, it is necessary to predict the object motion from the visual information. This paper proposes the prediction method considering object motion based on visual servo system. By using this method, the robot predicts the goal position which is the stop position of the movable object. Thereafter, the robot walks to the above prediction position. The robot moves to goal position without useless trajectory. The experiments with this prediction control method are conducted to confirm the validity of the proposed method. From these results, the validity of the proposed method is confirmed.

An integration method between vision-based disturbance observer and bilateral haptic system for robust tracking of target object

This paper presents a technique for a robust tracking of the target object by integration of the vision-based disturbance observer with bilateral haptic system. As for the motion navigation task, the bilateral control of master-slave system is combined with the vision-based force compliance controller. The disturbance of the modelling error that occurs in the integration of the system will be compensated by the proposed vision-based disturbance observer. The concept of control structure between the integration of bilateral manipulator, vision-based force compliance controller and the proposed vision-based disturbance observer are described. Two experiments were conducted to compare the result of without and with the proposed integration method. From the experimental results, the robustness of the proposed system is confirmed.

Experimental comparison of design methods for equivalent mass matrix in motion control system based on workspace observer

This paper investigates a design method for an equivalent mass matrix in motion control based on workspace observer. The equivalent mass matrix implemented in the control system is often designed as a diagonal matrix. On the other hand, a real equivalent mass matrix includes non-diagonal elements. Conventionally, assuming the cut-off frequency as infinity, these elements is ignored. However, actually, since the cut-off frequency is not infinity, the non-diagonal elements can not be ignored. Therefore, in order to improve the control performance, it may be necessary to implement the equivalent mass matrix including the non-diagonal elements. From the background, the experimental comparison about the equivalent mass matrix design is conducted.

Point-to-point motion control based on reproduction of recorded human motions with time scaling

In order to assist human beings, the reproduction methods of the recorded human motions have been researched. On these systems, the human motions are recorded as the haptic data (i.e., position, velocity, and force data) by using bilateral control. However, these conventional methods show poor adaptability to the difference in the environmental location during the reproduced phase. In order to compensate this spatial difference, the spatial data processing of the recorded human motions was utilized. On the other hand, the reproduction method of the recorded human motions with time scaling is proposed to compensate this spatial problem in this paper. In other words, the proposed method applies time scaling to compensate the spatial difference. For the realization of the proposed reproduction method with time scaling, the recorded velocity and force data are utilized. By using the proposed method, the physical meaning is clear compared with conventional methods, since power on the certain moment of the reordered task is reproduced. This paper focuses on the point-to-point motion, which includes the force motion and the position motion, as one of typical tasks in the industry field. The validity of the proposed method was confirmed by the experimental results.

Large driving range increase of series chopper based power train using motor test bench

Authors proposed the series chopper based power train aimed for the extension of the driving range. In previous paper [1], under the condition of the constant DC-supply voltage, effectiveness of the optimization of the profile of the chopper output voltage was shown. However, the output voltage of the battery used in the actual EV varies depending on the state of charge (SOC). Because of this difference, the precise comparison of the power train was not performed. In this paper, by emulating the battery including the internal resistance and output voltage dependency on SOC, the driving range is compared in the motor test bench. It is shown that the chopper output voltage adjustment depending on the rotor speed and the weight of the chopper has large effect on the driving range. In comparison to non-chopper power train, the driving range of the series chopper power train increases by 2.1%. In addition, by decreasing the weight of the chopper by a half and zero, the driving range further extends by 1.4% and 3.0%.

A synchronization method of visual and tactile information by virtual slave model in bilateral control

This paper proposes a synchronization method of visual and tactile information by using a virtual slave model in a bilateral control. Considering an actual remote-operated system, an operator operates a master system while watching visual information that is sent from a slave side. However, transmission of position, force, and visual information has communication delay. This is because the slave system on the image moves later than the actual slave system. This communication delay gives a bad effect on operability in the bilateral control. Therefore, the synchronization method of visual and tactile information is important. From this viewpoint, visual and tactile information in bilateral control is synchronized by using the virtual slave model. This virtual slave model is overlaid on the image from the slave side. The operator operates the master system while watching the virtual slave model overlaid on the image. As a result, the operability is improved, since the virtual slave model helps the communication delay of visual information. The effectiveness of the proposed system was confirmed form the experimental results.

Motion navigation in haptic bilateral system based on vision-based force compliance controller taking object coordinate into account

This paper addresses a solution for solving the objects rotational effect during the navigation process by the haptic bilateral control system. The system utilizes the vision-based guidance which depends on the virtual force generated by the vision-based force compliance controller (VFCC). During objects navigation, the virtual force is generated and affected to the manipulators horizontal trajectory movement. In this paper, the different rotational angle of an objects trajectory which reflects to different movement direction of produced force, will be studied and evaluated. The details concerning the implementation of this method will be discussed. Two sets of experiments are conducted to evaluate the effectiveness of the proposed technique.

Virtual force generation method for remote control system in mobile robot

This paper describes a remote control system with a virtual force feedback in a mobile robot. In the mobile robot, a laser range finder is utilized to recognize environmental information. By using this environmental information and the specification of the mobile robot, the safety velocity area (SVA) is calculated in real-time. On the other hand, an operator generates the velocity commands for the mobile robot in real time. By using the relation between SVA and the velocity commands, the virtual force is generated. If the velocity commands are out of SVA, the operator can feel the virtual force. In the previous research, the virtual force is generated based on the only velocity differences. Therefore, the chattering of virtual force commands may occur. In order to solve this problem, this paper proposes the virtual force generation method with hysteresis. Therefore, the operability of the remote control system is increased. From experimental results, the validity of the proposed method was confirmed.