Acquisition of information about the environment around a mobile robot is important for purposes such as controlling the robot from a remote location and in situations such as that when the robot is running autonomously. In many researches, audiovisual information is used. However, acquisition of information about force sensation, which is included in environmental information, has not been well researched. The mobile-hapto, which is a remote control system with force information, has been proposed, but the robot used for the system can acquire only the horizontal component of forces. For this reason, in this research, a three-wheeled mobile robot that consists of seven actuators was developed and its control system was constructed. It can get information on horizontal and vertical forces without using force sensors. By using this robot, detailed information on the forces in the environment can be acquired and the operability of the robot and its capability to adjust to the environment are expected to improve.
In this paper, the range extension control system based on the least squares method is proposed for electric vehicles with in-wheel motors and front active steering. We propose a method that distributes front and rear wheel sideslip angles and the difference in the driving force between the left and right motors because of the lateral force and yawmoment. The proposed method enables a reduction in the driving resistance generated because of the front steering angle. In fact, the mileage per charge is increased to about 200m/kWh. Simulations and experiments are carried out to confirm the effectiveness of the proposed method.
Recent advances in control technology have contributed to the development of robot systems for communication. Robot systems recognize their environment on the basis of audio-visual information. Recognition methods based on audio-visual feedback have been developed by many researchers. Apart from auditory and visual information, haptic information has recently attracted attention as the third type of multimedia information. The sense of touch is useful for remote manipulation. Feedback of haptic information is realized by bilateral control. In conventional research, most systems are constructed using a master-slave system in which the master-slave systems have the same mechanical structure. However, very few studies have been carried out on force feedback systems with different mechanical structures. This paper proposes a novel control method for mobile-hapto, which involves force feedback using mobility systems. In this study, the mobile-hapto consists of a mobile robot that can move in an infinite area for motion and a joystick that is fixed at a given position and can be operated manually. To realize of force feedback in the mobile-hapto, a modal transformation matrix for bilateral control is proposed. The proposed modal transformation matrix is able to change the dimension of the controlled value. The joystick is treated as a pedal by changing two dimensions of the mobile robot position. The mobile-hapto is possible to be subjected to intuitive manipulation. The validity of the proposed method is experimentally verified.
This paper proposes a new fine-motion-control method for realizing high-accuracy and high-speed contact motion of industrial robots by employing sensorless force control. Today, although industrial robots have become considerably important in the modern industrial society, their functions are limited. A typical limited function is the positioning motion control of robots used in the manufacturing industry. Contact motion is necessary for almost all new applications. In this study, by employing the proposed motion control, smooth and quick contact motion of industrial robots is realized by using a sensorless I-P (Integral-Proportional) force feedback controller. The proposed method is simple and effective, takes into account both the inertia of a robot and the behavior of the I-P force controller. In the experiments, a three-degree-of-freedom robot is brought into contact with an object (a concrete block or a rubber board) by the I-P force control using the proposed method. Further, in the experiment, the motion of the robot's end-effector was considered. The validity of the proposed method is confirmed by using a six-axis force sensor and an acceleration sensor in the contact motion experiments.
Presently in the industry, temperature control and heat flow control are conducted for many thermal devices, including the Peltier device, which facilitates heat transfer on the basis of the Peltier effect. Generally, temperature control compensates for the heat flowing from the external environment, while the heat actively flows into the system during heat flow control. Thus, temperature control and heat flow control differ from each other. However, there have been no detailed discussions on a thermal control process in which the thermal conductance of control ranges between 0 and ∞. This paper focuses on the thermal conductance of control and the construction of a thermal conductance control system for a Peltier device using a heat disturbance observer. When using the thermal conductance controller, the thermal conductance of control is altered, and the system becomes thermally compliant with the external environment. This paper also shows the experimental results that confirm the validity of the proposed control system.
Versatile and safe manipulators are required for use in human environments. A tendon mechanism with nonlinear springs that can mechanically adjust joint stiffness is one candidate that can satisfy the requirements of versatility and safety. In this paper, a hybrid stiffness ellipse control for controlling both mechanical and control stiffness at the end of the manipulator is proposed for the tendon mechanisms. This study shows the transformation of the stiffness ellipse at the ends of arms to joint stiffness. The transformation is applied to both mechanical joint stiffness and controller gain of joint angle controller. Simulation results verify the validity of the proposed method.
This paper proposes a control system for suppressing tracking error offset and multiharmonic disturbance in high speed optical disk systems. Residual tracking error consists of primary harmonics, high-order harmonics, and offset. Therefore, this paper proposes a tracking control system for suppressing residual tracking error, including primary harmonics, high order harmonics disturbance, and offset. The cause of the offset included in the residual tracking error is discussed. The cause is found to be the operation error in the fixed-point DSP (digital signal processor) and the phase lag of the LPF (low pass filter). Moreover, the proposed control system is designed for two types of high-speed optical disk system. The experimental results show that the proposed system enables an optical disk system to achieve a fine tracking performance.
It is desirable for a container crane to operate smoothly and quickly. For this purpose, the control system of a container crane should be capable of anti-sway control for suppressing vibrations. A vision sensor system is often used to detect the sway angle. However, since a control system with a vision sensor has a delay time when determining the angle, it sometimes leads to the deterioration of the control performance owing to the delay time. In order to overcome this problem, this paper proposes a new anti-sway crane control system based on a dual-state observer with sensor-delay correction. However, because of nonlinear friction in the crane, the estimation accuracy achieved by using the observer is poor. To overcome this problem, this paper proposes a disturbance observer considering friction disturbance. The control performance and effectiveness of the proposed robust control system based on the estimated information are confirmed to be satisfactory from experimental results.
In recent years, several methods for decomposing the whole motion of a parallel multi-degrees-of-freedom (MDOF) system into motion modes have been proposed. A motion mode is a motion element that corresponds to a specific physical action, such as grasping, manipulating, and rotating. Modal decomposition is effective for the expression and analysis of a complicated motion. However, conventional methods can extract motion modes only if the arrangement of actuators in the system has spatial linearity and symmetry. Therefore, the actuators cannot be arranged arbitrarily when the conventional methods are applied. In order to solve this problem, a novel method for modal decomposition is proposed; this method is based on the discrete Fourier series expansion. The proposed method is applied to a parallel MDOF bilateral system in which the arrangement of actuators is spatially asymmetric. Finally, the validity of the proposed method is confirmed on the basis of the experimental results.
In the field of teleoperation, visual or tactile information obtained by the operators is restricted (e. g., limited or delayed sight) because of communication constraints. Therefore, it is difficult for the operators to operate the system. In this paper, a bilateral control system using the environmental information about the position and posture of a target as obtained by a camera is proposed. The proposed method reduces the workload of the operators by taking some of their tasks. An experiment is conducted to prove the benefit of the proposed method by using a 1-DOF master robot and a 2-DOF slave robot.
This paper describes a new method for the deployment of wireless relay nodes. When using rescue robots in a building or underground city, the wireless radio signal is attenuated significantly, and therefore, multi-hop extension involving wireless communication relays is required. The goal of this research is to deploy wireless relay nodes to maintain connectivity between the base station and the leader robot that explores around the front line. To move the relay robot autonomously, a distributed algorithm is required. The proposed method is suitable when it is applied for wireless relay purposes. In the method, a virtual force drives a node to the centroid of Voronoi neighbors, and it maintains the connectivity of wireless communication. The proposed method is evaluated by conducting numerical simulations and experiments. In the simulation, one or two leader robots are assumed. In the experiment, a mobile robot equipped with omni-wheels is used.
This paper describes the application of a magnetic gear to a robot by fulfilling the essential requirements for a robot control, which are velocity control, position control, and force control. A magnetic gear is a transmission device that realizes contactless torque transmission by applying a magnetic force. When using a magnetic gear, cogging torque and spring characteristics need to be considered. In this paper, we introduce an approximate model of cogging torque. This model is used for velocity control to attenuate the disturbance due to cogging torque. In the case of position control, the oscillations due to the spring effect of the magnetic attractive force become a problem. To reduce the adverse effect due to these oscillations, resonance ratio control is applied. We also propose to use a magnetic gear for realizing the force sensorless bilateral control of teleoperation. Thanks to the frictionless transmission of a magnetic gear, the force sensorless estimation of a reaction force can be realized using a reaction force observer.
In this paper, a novel mechanism and a controller for two-link manipulators with two monoarticular muscle mechanisms and one biarticular muscle mechanism are proposed. The monoarticular and biarticular muscle mechanisms are actuated by eight flexible actuators that consist of one linear motor and one thrust wire. The validity of the mechanism and controller is confirmed by experiments.
This paper deals with the shaft end-to-end voltage resulting from asymmetric stray capacitances in an inverter-driven motor. The origin of the voltage can be any of the following: a ground leakage current, dielectric breakdown in bearings, and asymmetric stray capacitances on stator windings. The third origin seems to be related to the differential-mode current, but the details of the relationship have not been clarified. In this study, differential-mode tests are carried out on an ungrounded motor rated at 400V and 15kW, and the shaft end-to-end voltage generation by the asymmetric stray capacitances is theoretically discussed. Finaly, a winding model is presented for the purpose of understanding the mechanism responsible for the shaft end-to-end voltage.
This paper describes the estimation of the optimal measurement position by discriminant analysis based on Wilks' lambda for myoelectric hand control. In previous studies, for motion discrimination, the myoelectric signals were measured at the same positions. However, the optimal measurement positions of the myoelectric signals for motion discrimination differ depending on the remaining muscles of amputees. Therefore, the purpose of this study is to estimate the optimal and fewer measurement positions for precise motion discrimination of a human forearm. This study proposes a method for estimating the optimal measurement positions by discriminant analysis based on Wilks' lambda, using the myoelectric signals measured at multiple positions. The results of some experiments on the myoelectric hand simulator show the effectiveness of the proposed optimal measurement position estimation method.
This paper proposes a current controller for signal-injection-based control schemes such as those for parameter identification and position sensorless control. In a conventional current control system with voltage signal injection, the separation of the injected frequency components from the current is carried out by using band stop filters. However, the separation is not accurate, especially when the system is in the transient state and/or when the current controller bandwidth is close to the injected signal frequency. This leads to the distortion of the transient response and affects the stability of the current control system. The proposed controller estimates the injected frequency components in the current on the basis of a motor model by using the injected signal as the input. Therefore, accurate signal separation is accomplished even in the transient state. Moreover, the current controller's stability and dynamic performance are improved significantly. Experimental results are presented to validate the proposed method. Factors that play an important role in the implementation of the controller, such as time delay and parameter variation, are discussed.
This paper describes a new method for a rotor position sensorless control of a surface permanent magnet synchronous motor based on a model reference adaptive system (MRAS). This method features the MRAS in a current control loop to estimate a rotor speed and position by using only current sensors. This method as well as almost all the conventional methods incorporates a mathematical model of the motor, which consists of parameters such as winding resistances, inductances, and an induced voltage constant. Hence, the important thing is to investigate how the deviation of these parameters affects the estimated rotor position. First, this paper proposes a structure of the sensorless control applied in the current control loop. Next, it proves the stability of the proposed method when motor parameters deviate from the nominal values, and derives the relationship between the estimated position and the deviation of the parameters in a steady state. Finally, some experimental results are presented to show performance and effectiveness of the proposed method.
The contributions of this study are the proposal of a distance sensor based on magnetic resonance coupling with a novel configuration and error evaluation of the proposed sensor. Since the measuring device and their batteries are connected to the target side in conventional distance sensors based on magnetic resonance coupling, the batteries need to be changed during long-term operation. Therefore, in this paper, a distance sensor that integrates the measuring device into the transmitter side is proposed; in this sensor, external attachments or batteries on the target side are not required. In addition, the distance error in the proposed sensor is evaluated by theory and experiment. In these evaluations, the effect of the Q factor on the relation between the distance error and the distance is the main consideration. Apparently, high-Q-factor antennas can reduce the distance error for long distances but increase the error for short distances. The obtained result can be used as a guideline for designing distance sensors.
A series-type multiple-dc-inputs direct electric power converter (D-EPC) has been developed. The D-EPC is a multiple-dc-inputs inverter, and it can eliminate the need for a dc/dc converter that is generally used in conventional converter/inverter systems. The original D-EPC has two positive terminals and a negative terminal in common. Each upper arm between the positive terminal and the ac output is built with a bidirectional switch to prevent short circuit. In the series-type D-EPC, the input power sources are connected in series, thus, the number of bidirectional switches can be reduced and the series voltage can be used in the motor drive system. A new pulse width modulation (PWM) generation technique to drive switching devices in the series-type D-EPC has also been developed. Tests have confirmed that the motor can be operated by controlling the power distribution and that a series voltage can be used.
A single-phase current source converter with variable voltage and constant frequency is presented. The converter is a single bridge circuit of two legs and has a smoothing reactor in the dc side. The power source and the load are connected in series and they are connected to the bridge legs. The normal PWM method with the sinusoidal modulating and the triangular carrier waves is employed for the converter. The experimental results confirm that the PWM converter has the sinusoidal voltage and current in both the source and the load.
In contactless power transfer systems, to improve the power factor, a compensator is implemented in the secondary of the system. However, the conventional compensators, for example, LCL compensator, can not work efficiently when the secondary is connected with diode rectifier. This paper proposes a power factor compensator that can work even in this case. The simulation results prove the effectiveness of the proposed compensator.
This paper describes the life of noise of bearing electro-erosion in the shaft voltage of brushless DC motors. We confirmed that shaft voltage is suppressed to equal to or less than the dielectric breakdown voltage of bearing lubricant in the insulated rotor proposed for suppression of shaft voltage. However, since bearing electro-erosion appears over time along with the deterioration of noise performance, the threshold of the shaft voltage to secure noise performance over long periods of time is necessary. Therefore, the threshold of the shaft voltage that influences the life of noise was obtained in acceleration tests.