The first IEEE International Workshop on Advanced Motion Control was held in 1990 pointed out the importance of physical interpretation of motion control. The software servoing technology is now common in machine tools, robotics, and mechatronics. It has been intensively developed for the numerical control (NC) machines. Recently, motion control in unknown environment will be more and more important. Conventional motion control is not always suitable due to the lack of adaptive capability to the environment. A more sophisticated ability in motion control is necessary for compliant contact with environment. Acceleration control is the key technology of motion control in unknown environment. The acceleration control can make a motion system to be a zero control stiffness system without losing the robustness. Furthermore, a realization of multi-degree-of-freedom motion is necessary for future human assistance. A human assistant motion will require various control stiffness corresponding to the task. The review paper focuses on the modal coordinate system to integrate the various control stiffness in the virtual axes. A bilateral teleoperation is a good candidate to consider the future human assistant motion and integration of decentralized systems. Thus the paper reviews and discusses the bilateral teleoperation from the control stiffness and the modal control design points of view.
This paper proposes a unified control approach for multi-robot systems by interaction mode control. The proposed interaction mode control considers only the interactions between the systems. The interactions are abstracted by using the quarry matrix. Since the transformed modes are independent to each other, it is possible to design controller in the modal space. This paper also proposes a novel control index named “hybrid ratio”. The hybrid ratio is defined as the influence of the external acceleration input to the acceleration response of the system. Since it is possible to realize the assigned hybrid ratio in each mode according to the task, the motion command with the hybrid ratio is represented as the task code. Furthermore, the task code is able to be changed during the motion. Thus, the interaction mode control is treated as the task kinematics. As a result, intuitive and flexible controller design is attained by the proposed method. The proposed interaction mode control is applied for cooperative transportation by multi-robot systems. The experimental results show viability of the proposed method.
In this paper, we present a control scheme of grasping and manipulation using mode transformation and a four-channel grasping/manipulating controller based on the control scheme. A second-order discrete Fourier transform (DFT) matrix is utilized as a mode transformation matrix. By means of the control scheme, a grasping controller and a manipulating controller can be designed independently in a grasping mode and a manipulating mode, respectively. In addition, we also propose a novel control method that combines the four-channel bilateral controller and the four-channel grasping/manipulating controller. This proposed controller makes it possible to select a proper mode depending on each situation, for example, bilateral grasping control. In the bilateral grasping control system, the manipulating mode is position-controlled locally in each side (master side and slave side), and the grasping mode is controlled bilaterally between master side and slave side. The validity of the proposed methods is shown by the experimental results.
In this paper, a noble bilateral control method is introduced to realize decoupled haptic transmission technology. At first, bilateral system based on acceleration control is discussed. Both of master and slave are controlled by position regulator and force servoing, and these two controllers are decomposed into two modes “common mode” and “differential mode” in the virtual space. Decomposed controller helps to control position and force information individually. Second, the bilateral control is extended and generalized as a multilateral control, which based on the decomposed controller. Third, to realize decoupled haptic information, IR (identity ratio) is introduced into differential mode. IR shows ratio of each input in the common mode. Although slave robot is controlled by a numbers of masters, each of masters can feel the sense which depend on their inputs. Fourth, numerical simulation and experimental results are shown. The numerical simulation and experimental results show the viability of the proposed method.
The disturbance observer can observe and suppress the disturbance torque within its bandwidth. Recent motion systems begin to spread in the society and they are required to have ability to contact with unknown environment. Such a haptic motion requires much wider bandwidth. However, since the conventional disturbance observer attains the acceleration response by the second order derivative of position response, the bandwidth is limited due to the derivative noise. This paper proposes a novel structure of a disturbance observer. The proposed disturbance observer uses an acceleration sensor for enlargement of bandwidth. Generally, the bandwidth of an acceleration sensor is from 1Hz to more than 1kHz. To cover DC range, the conventional position sensor based disturbance observer is integrated. Thus, the performance of the proposed Position and Acceleration input based disturbance observer (PADO) is superior to the conventional one. The PADO is applied to position control (infinity stiffness) and force control (zero stiffness). The numerical and experimental results show viability of the proposed method.
In motion control, position control systems of servomotors are generally designed without considering a current loop and dynamics of a PWM inverter. In this paper, a novel precise model of servomotor is developed including the current loop and the PWM inverter, and the high-speed servo system is proposed based on perfect tracking control with the precise model. Finally, simulations and experiments are performed to show the advantages of the proposed method.
In this paper, what we want to do is to develop an observation device to measure the working radius of a crane truck. The device has a single CCD camera, a laser range finder and two AC servo motors. First, in order to measure the working radius, we need to consider algorithm of a crane hook recognition. Then, we attach the cross mark on the crane hook. Namely, instead of the crane hook, we try to recognize the cross mark. Further, for the observation device, we construct PI control system with an extended Kalman filter to track the moving cross mark. Through experiments, we show the usefulness of our device including new control system of mark tracking.
Industrial robot with two-inertia model and resonant vibration suppression by using parameters from resonant identification method are addressed in this paper. By using only D-PD control with vibration suppression scheme for two-inertia model of flexible joint robot, the end-effector position does not perfectly reach the desired position owing to the effect of external force to the elastic arm. However, only gear stiffness parameter of two-inertia model is not enough, the new equivalent spring constant parameter including the stiffness of link and gear of the robot is introduced as the total arm spring constant. The novel load-side disturbance compensation considering total arm elasticity is proposed in this paper. The proposed control system is based on inner-loop vibration suppression feedback control and load-side disturbance suppression which motivates the simple consideration of the elastic joint under external torque. Moreover, the experimental results show the effectiveness of the proposed robust position control of end-effector with disturbance compensation considering total arm stiffness. The experimentation on workspace impedance control with inner-loop disturbance suppression implementing on the three degree-of-freedom (3-DOF) robot manipulator is also presented and discussed. The performance and feasibility of the proposed position control of end-effector is confirmed to apply to industrial robot manipulator without additional device.
A novel remote monitoring system for all day outdoor observation using multiple wireless sensors and wireless communication (Handy phone and PHS) is proposed. The whole system consists of three parts: (i) a host station that is PC (Personal Computer), (ii) remote station that contains a camera controlled by CPU and power supply (battery attached by solar cell), and (iii) multiple wireless sensors having each ID signal. The remote station usually works by an event-driven method based on the wireless sensor signals. Because of this event-driven method, various multi-vision systems are easily configurable. This paper describes the details of the system and evaluates the possibility of the application of the system. Since some of the systems are now really running in many places, we can consider that the effectiveness of the system is shown by the fact in a practical sense.
This paper presents a practical residual vibration suppression methodology for the repetitive fast-response and high-precision positioning in laser drilling machines. The authors have already proposed an Initial Value Compensation (IVC) approach using addtional input, where two essential subjects have been remained: one was the input saturation in power amplifier, and the other was the performance deterioration due to the modeling errors. In the paper, improvement approaches in compensators are proposed, where the additional input within the power saturation can be applied to the robust feedback controller. The effectiveness of the proposed compensation has been verified by numerical simulations and experiments using a positioning device for galvano scanners.
This paper presents a command shaping technique based on a minimum jerk control approach considering a target position correction during motion, for the fast and precise positioning in vibratory mechatronic systems. The positioning controller is designed by a 2-degrees-of-freedom control: a feedback compensator is synthesized by H∞ control design to ensure the robust stability, while a feedforward compensator suppresses the vibration in response based on a coprime factorization expression of the plant mechanism. The command shaping, on the other hand, eliminates the corresponding vibration components of the primary and secondary modes in the position command, where the continuity of jerk component in the command can be ensured against the target position correction. The effectiveness of the proposed shaping technique has been verified by experiments using a table drive system on machine stand.
This paper presents an expression of system connection considering transmission delay. In a research field of decentralized system or information system, expression method of the system connection is very important issue. Therefore some expression methods of system connection have been proposed so far. However those expressions are mainly based on binary operation and can not consider the transmission delay on connection paths although the concept of time is efficient for expression of system connection. In this paper, expression methods of system connection considering transmission delays on the paths are proposed. Those expressions are based on exponential-type expression and can express both connections and transmission delays. Furthermore the expression that can express connections, transmission delays and past subsystems is also proposed. As one example of the application of proposed expressions, application for path selection of the design of network-based control system is described.
In this paper, we propose a visual tracking method for a moving object without tracking delay. On visual servoing, image-based method with image Jacobian is often taken for target-centering camera motion control because it does not require target's 3D position estimation and is robust to modeling errors and noises. In an ordinary visual servoing approach, it is assumed that the target object would be fixed in the workspace. Therefore, for the purpose of tracking to a moving target, the image errors always exist between the target position and camera optical axis, that is, the visual tracking delay. In our proposed method, the target object's 3D position is estimated with the technique based on triangulation on stereo vision system. Then, the moving velocity is calculated in the camera coordinate frame. The image Jacobian concerns the camera velocity with the target velocity in the image plane. Additionally, the target velocity in 3D workspace is also converted into the velocity in the image plane. The converted velocity compensates the camera velocity to compensate the camera motion delay. This approach enables to achieve non-delayed tracking for moving target.
This paper proposes a visual servo control method for exploring motion of eye-in-hand robot to recognize a three-dimensional object. Optimal motion is based on the strategy in which the position estimation precision of the feature points gets improved when the feature points move widely, and the optimal robot motion provides the widest transitions of the feature points per unit robot motion, so that the robot should be controlled to purse such motion. In addition, this paper describes the way to reduce a large number of calculation efforts. The validity of our approach is confirmed in the several experimental results.
We propose a spiral-type motor that has high thrust characteristics as a linear actuator. This motor generates torque around the axis and thrust in the axial direction only by electromagnetic force. It has little friction because no additional hardware is required for straight-line movement. This paper presents the concept of the spiral motor. The finite-element method (FEM) analysis certifies that this motor has high motor constant as same as High Density Linear Motor (HDL). We also study a method to compensate the thrust fluctuation of 5-pitch-stator 6-pitch-mover model
This paper proposes a PI control method adjusted by a genetic algorithm (GA) for an ultra-sonic motor (USM). In the proposed method, a proportional and an integral gains are adjusted using GA in order to compensate characteristic variations of the plant. The effectiveness of the proposed method is confirmed by experiments.
This paper describes design and trial manufacture of the linear generator, which can convert any mechanical vibration of an automobile to electric energy. A mover, which includes permanent magnets, is linearly driven through a stator, by vibrations. Nd Fe-B magnets in the mover are placed as same magnetic poles face mutually, in order to make the change of magnetic flux in the coils of the stator. The coils are placed in the stator with same intervals of magnets. The coils are wound for the reverse to the next coil and they are connected series all. A magnetic material case covers the stator makes the magnetic flax is extended through the case and decrease canceling the flux in the coils of the stator. Numerical simulations calculated distribution of the magnetic field, electromotive force and driven power of the mover in order to determine the size of the linear generator. The linear generator and an experimental apparatus were produced on the basis of the simulation, and its performance was tested by experiments. The produced linear generator was confirmed to be useful as an onboard auxiliary power supply.
This paper proposes a new current balancer in single-phase three-wire secondary distribution systems using the correlation coefficients. The components of the load currents correlative to the primary side voltage waveform, which correspond to the active currents, are detected in each feeder, then the non-active and unbalanced-active components are compensated on the source side. The balanced currents with unity power factor are obtained in each feeder. The basic principle of the proposed method is discussed in detail, and then confirmed by digital computer simulation. A proto-type experimental system is constructed and tested. Experimental results demonstrate that the balanced source currents with unity power factor are obtained in spite of unbalanced load currents.
In general, the power transistor and IGBT are used in the switching power supplies for Xenon Arc Lamp as power switching devices. Today it is demanded to simplify the switching power supplies. As the switching frequency becomes higher, simplification of the switching power supply can be attained. But the power transistor and IGBT cannot be used for high-frequency power switching applications. Therefore we propose to use the power MOSFET and its parallel operation. This paper presents considerations on circuit composition of power supply for xenon arc lamp.