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This paper focuses on controlling the load-side acceleration (LSA) of a two-inertia system with the LSA. Here, an LSA control-based system on integral-proportional (I-P) drive-side velocity control is proposed for an industrial robot with mechanical resonance. The LSA control based on I-P drive-side velocity control with a two-inertia system adopts a wideband acceleration sensor capable of acquiring direct current (DC). The proposed structure is similar to that of the control system that adopts the disturbance observer (DOb)-based acceleration control of a single-inertia system as a minor loop. In addition, the proposed LSA control system comprises a drive-side velocity controller and load-side velocity disturbance observer, which are employed to simplify the plant system and, compensate for the velocity disturbance on the load-side, respectively. Furthermore, the limitations of the conventional acceleration controller and the effectiveness of the proposed LSA controller are verified via theoretical analysis, numerical simulations, and practical experiments.

In a two-inertia system, load-side control is relatively simple to design using a cascade controller with a torsion torque controller in the minor-loop. However, the control bandwidth of the outer controller, such as the load-side reaction force controller, is affected by the bandwidth of the minor-loop. Thus, this paper proposes load-side reaction force control based on model-matching control. To realize a simple model-matching control, an equivalent disturbance compensator (EDC) is applied to torsion torque controller. The EDC is able to be used to suppress disturbance, such as the reaction force to the torsion torque. Moreover, the torsion torque and environmental vibration mode are separated. The effectiveness of the proposed control is verified through numerical simulations and experiments.

To realize vibration suppression for a three-inertia system, this paper proposes a current control system using resonant frequency damping disturbance observer based robot servo system. The resonance frequency components for achieving vibration suppression is estimated by resonant frequency damping disturbance observer. Through the proposed current control system, vibration suppression is achieved against a three-inertia system. The effectiveness of the proposed method is confirmed through experiments

Load-side acceleration sensing based on load-side acceleration control is proposed for a two-inertia resonance system. The proposed method is divided into two stages. In the first stage, the feedback component from the load-side is canceled using the estimated value of the instantaneous state observer and the load-side acceleration. The two-inertia resonance system is converted into a simple second-order system using this method. The proposed method configures a control system of cascaded loops for the second-order system. Therefore, the load-side acceleration control is achieved by two specified bandwidths. The proposed method is easy to implement for conventional robots and yields superior cost-savings compared with other types of load-side acceleration control. The effectiveness of the proposed load-side acceleration controller is verified by theoretical analysis, numerical simulations, and experiments.

This paper proposes a back-forward drivable control based on torsion torque control (TTC) that achieves both back-forward drivability and vibration suppression for a two-inertia system. The proposed system combines the TTC that consists of I-P controller and velocity deviation feedback and a motor-side normalization compensator (MNC) to facilitate human-robot interactions. For the velocity deviation estimation, load-side torque observer (LTOB) and load-side velocity observer (LVOB) are evaluated on estimation performance. The better observer is applied to the TTC from the analysis results. The effectiveness of the proposed control system is verified by simulation and experimental results, and the vibration of the back-forward drivable response is considerably suppressed.

In previous research, the back-forward drivability of load-side torque control system based on a motor-side acceler­ation control has proven to be high, but contact motion has not yet been realized in human-robot interaction such as powered exoskeleton and direct teaching. To address this issue, this study proposes a load-side torque control system that achieves both bouncing suppression and human-interaction. This paper focuses on load-side acceleration because the bouncing motion at environmental contact and the human-robot interaction motion are able to be evaluated to its performances intuitively. Human-robot interaction is applied in low-frequency, and bouncing suppression is applied in high-frequency. The experimental results verify the effectiveness of the proposed method.

To operate two-inertia systems with high speed and precision, a control method to suppress mechanical resonance is required. A conventional current control system consists of a proportional integral controller and decoupling controller, and the conventional current control system has high motor torque control performance. However, the conventional current control system tends to excite mechanical resonance. This paper proposes a new current control system to suppress the resonance of a two-inertia system by using the cross-coupling term of a surface permanent magnet synchronous motor. The proposed control system consists of a proportional controller and voltage disturbance observer to estimate the voltage disturbance without including the cross-coupling term that is used as a damping control. The effectiveness of the proposed control system is validated by numerical simulations and experiments.

This paper considers the contact phase in a sensorless torque control system for a two-mass system. A plant system is a two mass system with an environmental switch. The environmental switch is used for considering unstable contact behavior. The state observer (SOB) and zero-order disturbance observer (ZODOB) are used to estimate the state variable of a plant system. In sensor-less torque control system, the ZODOB has better performance than the SOB. When plant system is not in contact with the environment the estimated value using the SOB is not good for control system. It makes control system becomes instability in some cases. When the ZODOB is fed back to torque control system, the stability of control system is preserved. Experiments are performed to confirm the effectiveness of using the ZODOB in sensor-less torque control system.

SUMMARY This study proposes a variable dynamic threshold for a jerk signal for achieving contact detection in industrial robots. Sensorless force control is useful in applications in advanced industrial robots. The external torque of each joint is estimated accurately by using a disturbance observer and by inverse dynamics calculations. However, the phase lag of the disturbance observer and the dynamic parameter error create force estimation errors. These errors hamper quick and reliable contact detection in industrial robots. Therefore, this study proposes a useful approach to contact detection that uses a variable dynamic threshold for a jerk signal. The proposed variable dynamic threshold reduces contact detection failures caused by force estimation errors during the free motion of a robot. The proposed threshold is suitable for robot motion and improves the speed of contact detection. Numerical simulation results show that the proposed method is valid for the parameter variations in an actual industrial robot. In addition, experimental results show that the dynamic threshold is a useful technique for application to general robot systems as well. The dynamic threshold is useful in applications for any industrial sensorless force control system.

In order to realize a fine force sensorless force control, this paper proposes a new notch-type friction-free disturbance observer(DOB) and a new notch-type friction-free reaction force observer(FFRFO). Generally, a force sensorless force control system always has influence on static friction phenomenon. To overcome this problem, this paper proposes a new force sensorless control system using the notch-type friction free reaction force observer, whose inner system is the proposed acceleration control based on the notch-type friction free disturbance observer. The effectiveness of the proposed system is confirmed by experiments using an actual industrial robot.

Industrial robots are required to perform high-speed and high-precision motion. Industrial robots are controlled using a conventional PI velocity controller with state feedback system for a two-inertia system. In general, the axis is modeled as a two-inertia system. However, a three-inertia system is required for modeling the axis because the industrial robot is required to have more high-performances motion. This paper proposes a vibration-suppression control system for a three-inertia system based on a PI velocity control system with state feedback system using the two-inertia approximation model. The new two-inertia system for the state observer is designed as an approximation model based on the three-inertia system. The effectiveness of the proposed system is confirmed by numerical simulations and experiments.

Recently, the scaling up of the storage capacity and data transfer rate of digital storage media has been required. However, increasing in the storage capacity and transfer rate makes optical head control more difficult. Thus, a tracking control system for optical discs must exhibit a high degree of precision control. Consequently, a new two-stage feedforward control (TSFFC) system for high-precision control is proposed in this paper. The proposed system is constructed using two zero phase error tracking (ZPET) control systems based on error prediction and an error-based disturbance observer (EDOB) that uses a notch filter to suppress non periodic disturbances. The proposed control system is designed for DDU-1000 for digital versatile discs (DVDs). The experimental results demonstrate that the proposed system effectively suppresses tracking errors.

This paper proposes a robust position control based on state feedback using double disturbance observer for two mass system. In load-side position control based on state feedback using disturbance observer, performance of control system is depend on bandwidth of disturbance observer. To solve problem, the load-side position control using I2-PI controller based on state feedback is proposed. The proposed system consists of PD position controller, motor-side acceleration controller, I2- PI controller equivalent of states feedback, velocity deviation feedback, and a zero-order load-side disturbance observer (ZLDOB) with variable noise-covariance (VNC) Kalman filter. The simulation and experimental results confirm that the load-side position control using I2-PI controller based on state feedback reduces the vibration in response load-side position. Additionally, the proposed method reduces the vibration in response load-side acceleration.

Currently, a high-precision tracking control system is needed for large-capacity optical disc drive system. This paper proposes a new full field-programmable gate array (FPGA) tracking control system based on an Error-Based Communication Disturbance Observer (ECDOB) with consideration of a time delay of the optical disc drive system. The FPGA control system sometime has a large influence on both the integer time delay and the non-integer time delay of the control system. In order to consider the time delay, this paper reconstructs the feedback control system by using the limited pole placement method. Moreover, this paper proposes a new error based communication disturbance observer. The experimental and numerical simulation results confirm that the tracking performance of proposed system is better than that of conventional feedback control system. In full FPGA tracking control of optical disc systems, the proposed error-based communication disturbance observer based tracking controller exhibits good performance.

This paper proposes a force control system including contact process using acceleration-sensor-based instantaneous state observer for high-stiffness gear drive. The proposed system is structured by PI velocity control system and IP force control system based on resonance ratio control system. An instantaneous state observer is used to a resonance ratio control system for a high-stiffness gear drive. In proposed system, the robot arm of a high-stiffness gear drive is achieved to move closer to the environment by using PI velocity control system. Moreover, the robot arm is achieved to come in contact with the environment by using IP force control system. Additionally, the force control system including contact process is needed a smooth switching of these control system, and smooth force control. To achieve the smooth switching of control system, an initial value of an integrator of force control system is calculated by the condition that a motor-side torque reference is constant when switching the control system. In addition, the algorithm is proposed to achieve the smooth force control system. The proposed method is achieved the smooth switching of control system and smooth force control system. The effectiveness of proposed method is confirmed by numerical simulation and experiments.

This paper compares performance of a double feedforward control system that considers for time delay. Recently, digital content size continues to increase. In order to cope, manufacturers of digital storage media try to increase capacity by narrowing the track pitch of these digital storage media. This digital controller designs and implements in a Field-Programmable Gate Array (FPGA). However, the control system includes non-integer the time delay. The time delay element exists in its characteristic polynomial. Therefore, the system is possibly destabilized by time delay. In the feedforward system, the feedforward compensation value is delayed by time delay. Considering these factors, a high-precision pickup control system that considering time delay is needed for optical discs. This paper proposes a new double feedforward control system considering time delay. In this paper, the tracking performance of the control system is compared to the conventional feedback control system and the new error based communication disturbance observer. In optical disc systems, the proposed double feedforward control system considering time delay has a good performance.

To achieve force control of an industrial robot, this paper proposes an I-PD force control system based on an instantaneous state observer. The structure of the proposed system is based on a resonance ratio control system and a feedback signal of the reaction force response. In this paper, the gain of a pseudo derivation is designed as the feedback gain. From the results of the designed gains, the feedback gain Kf is a negative value. Hence, the resonance ratio control system becomes equivalent to a state feedback. For the stability of the proposed I-PD force control system based on the acceleration control system and a state feedback, a new analysis method is required. This paper analyzes an open-loop of the proposed system considering the bandwidth of the observer. The results of an analysis show that an observer with a wide bandwidth is required. Therefore, the parameters of proposed system using the instantaneous state observer are designed based on the coefficient diagram method. The effectiveness of the proposed method is confirmed by performing numerical simulations based on the model of an industrial robot arm. The results show that the proposed method is effective for the stable force control of an industrial robot arm.

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 antisway 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 deterioration of control performance owing to the delay time. In order to overcome this problem, this paper proposes a new antisway 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 shown to be satisfactory by experimental results. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 184(3): 36–46, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22412

An optical disk drive system must realize high precision tracking control. For this purpose, the tracking control system that combined a robust feedback controller and a zero phase error feedforward tracking controllertracking control system has been proposed. This proposed feedforward tracking control system effectively suppresses the tracking error caused by track eccentricity. However, it is sometimes difficult for a conventional feedforward tracking control system to realize high precision tracking control. Hence, this paper proposes a new perfect tracking control (PTC) system that uses a prediction state observer. Numerical simulation results and experimental results confirm that the proposed system effectively suppresses the tracking error for a disk rotation speed of 8000[rpm] and operates stably. Therefore, the proposed system realizes high precision tracking control.

This paper proposes the new design method of error-prediction control systems combining the ZPET control and the robust feedback control. The error-prediction control system based on ZPET control can reduce the tracking error caused by periodic disturbances more efficiently than the conventional repetitive control technique. However, the proposed tracking servo system does not reduce the residual tracking error caused by the low-pass filter of the feedforward compensation and by the long sampling time. In order to overcome this problem, this paper proposes the new structure of the feedforward tracking control system. The modified ZPET control tracking servo system for optical disk recording system does not include the low-pass filter and its sampling time becomes faster. On the other hand, the sudden disturbance observer reduces the influence of nonperiodic disturbances. The experimental results point out that the proposed tracking servo system has a precise tracking response against both the periodic disturbances and the nonperiodic disturbances. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(4): 51–59, 2010; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/eej.20800

This paper proposes a new robust feedforward tracking control system suppressing tracking error including harmonics disturbance and DC offset for optical disk recording system. The proposed tracking control system consists of triple compensation loops of tracking error which are the robust feedback control loop, a new harmonics disturbance suppression loop based on Zero Phase Error Tracking(ZPET) feedforward control and a new additional DC offset compensation loop. The feedback controller is the most inner loop which is based on the high gain servo system. The harmonics disturbance suppression loop based on ZPET control is the middle loop which suppresses the influence of many periodic disturbances. The final outer loop is a new additional DC offset compensation loop which suppresses the DC offset caused by ZPET feedforward control. The experimental results point out that the proposed system well realizes the fine tracking performance for optical disk recording system.

In the recent times, the number of amateur farmers has been increasing. Although amateur farmers use tillers, they may find it difficult to drive the tiller along a straight line. There is a need for electric tillers with independent drive wheels. This paper proposes straight control incorporating human driving input by using a disturbance observer. Numerical simulation results and experimental results confirm the validity of the proposed method.

This paper proposes a stable force control system to achieve the force control of industrial robots. The proposed stable force control system is designed by using an I-P force control system and a resonance ratio control system considering the required interaction with the environment. To design the resonance ratio control system considering the contact with the environment, this paper analyzes the stability of the proposed resonance ratio control and the bandwidth of a disturbance observer. This paper designs the resonance ratio control system using an instantaneous state observer considering the results of the stability analysis. In addition, a stable force control system is designed based on the resonance ratio control system using an instantaneous state observer. In this paper, the effectiveness of the proposed force control system is confirmed by performing numerical simulations and experiments using an industrial robot arm.

Recently, the data size of digital content has increased. To address the resultant storage issues, manufacturers have tried to increase storage capacity by narrowing the track pitch of digital storage media.[1] Considering all these factors, a high-precision tracking control system is required for optical discs. In this study, this paper develop and implement a feedforward control system using an trajectory command prediction mechanism to effectively suppress periodic components by fieldprogrammable gate array (FPGA). This paper proposes a zerophase error-tracking feedforward control system[2], [3] that considers the delay time component. This paper design and implement the propose control system for a test system, the ODU-1000 for Blu-ray, whitch is implanted in a digital signal processor (DSP). The results show that there is increased delay time because of the calculation time. In the configuration of the control system, this paper implement both feedback and feedforward control systems using a FPGA. The control system realizes high-speed control operation as a hardware controller. Experimental results obtain confirm that the propose system is practical and effective.

Recently, the data size of digital content has increased. In order to cope, manufacturers have tried to increase capacity by narrowing the track pitch of digital storage media. In addition, recent advancements in technology have resulted in a new optical disc that has a rotation speed of over 15,000 rpm. Considering all these factors, a high-precision pick-up control system is needed for optical discs. In this study, a feedforward control system using an error prediction mechanism to effectively suppress periodic components is implemented. However, the feedforward control system of a conventional pick-up control system does not consider the dead time delay component. This paper proposes a zero phase error tracking feedforward control system that does consider it. The propose control system is designed and implemented for a test system, the ODU-1000 for Blu-ray Disc, implanted in a digital signal processor (DSP). The results of experiments confirm that the propose system is practical and effective.

This paper proposes a new robust tracking servo system for the optical disk recording system with feedforward controller based on the prediction of the tracking error. In optical recording systems, the feedback servo system must suppress the influence of force disturbance and parameter variation. To overcome this problem, this paper designs the robust feedback control system by using coprime factorization and disturbance observer. The detecting signal of the optical disk recording system is only a tracking error. Hence, the feedforward controller of the proposed tracking control system is constructed based on both the "zero-phase-error tracking" control theory and the prediction of the tracking error. The experimental results point out that the proposed tracking servo system has a quick and precise tracking response and keeps the residual tracking error below its tolerance.

This paper proposes a new robust feedforward tracking servo system for optical disk recording systems in the case of a sudden disturbance for the optical disk recording system. In optical recording systems, the tracking servo system must suppress tracking error below its tolerance. This paper designs the robust feedback control system by using the coprime factorization and disturbance observer. The proposed robust feedback control system suppresses the sudden disturbance caused by walking and running. The detecting signal of optical disk recording systems is only a tracking error. Hence, the feedforward controller of the proposed tracking control system is constructed based on both Zero Phase Error Tracking (ZPET) control theory and prediction of tracking error. The experimental results point out that the proposed tracking servo system has a quick and precise tracking response and keeps the residual tracking error below its tolerance. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(4): 60– 68, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20257

In optical recording system, the tracking control system must follow the track of optical disk against the influence on the track eccentricity and the force disturbance. This paper proposes a new robust following control system with the proposed feedforward controller and the proposed sudden disturbance observer. The proposed feedforward controller is based on “Zero Phase Error Tracking” (ZPET) control using only the tracking error. The experimental results point out that the proposed robust following control system suppresses the influence on both periodic disturbance and sudden disturbance. Hence, the proposed robust following control system realizes the desired precise tracking control performance against both disturbances using only tracking error.

This paper proposes a realization of motion control based on dynamic torque compensation and two-degrees-of-freedom speed control system. In order to suppress the dynamic torque of robot manipulator quickly, this paper constructs the feedforward torque compensation method based on inverse dynamics calculation on each joint control system.Moreover, the proposed joint control system is constructed by the robust control system based on the state feedback, PI speed controller and feedforward controller.The proposed method can suppress the influence of inertia variation and torsional vibration of joint system quickly and completely.The simulation results and experimental results show that the proposed system well regulates the motion of multi-joint robot and suppresses the torsional vibration.

Injection molding is a common method for producing various resin products. The force control system of a typical injection molding machine obtains information about the force from the environment of the machine via a force sensor. However, because a force sensor often has disadvantages such as signal noise, high cost, and narrow bandwidth, a reaction force observer has been developed for electric injection molding machines. The high-order reaction force observer (HORFO) is developed which includes a friction compensation element and uses the dither signal insertion method. However, the static frictional force and dynamic friction force have been not considered in this reaction force estimation observer, and accurate force control is difficult because of estimation error. In this paper, we propose a new friction model that takes into account the stribeck effect in order to improve the estimation error problem in force sensorless estimation. In addition the effectiveness of the proposed method is investigated in actual experiments using an injection molding machine.

Pickup systems for optical disks operate in the horizontal and vertical directions for tracking and focusing, respectively. Control systems for optical disks consist of focusing control and tracking control for each operation direction. Therefore, this paper proposes a new minimum tracking & focusing trajectory control based on two-dimensional feedforward control system. Two-dimensional feedforward control system makes the error vector combined focusing error and tracking error. The error vector is the input variable into the feedforward compensator on the basis of a zero phase error tracking control. Because, it is difficult to perform high-speed sampling in a conventional two-dimensional control system, the proposed two-dimensional feedforward compensator can perform high-speed sampling, which is based on an equivalent-perfect tracking control. The experimental results show the effectiveness of the proposed control system.

To enhance the productivity and quality, high speed and high precision industrial robots are required. Industrial robots suffer a vibration caused by the axial torsion that adversely affects their motion control. In addition, the vibration of a joint is transfered to another joint because of the dynamic interferences with the robot manipulator. To overcome these problems, this paper proposes a new method for the link-coupled vibration suppression control for industrial robots, in which the product of inertia is considered. First, this paper shows a two-inertia model with a consideration that the product of inertia is a linear behavior. Hence, this paper proposes a new link-coupled vibration suppression control system, which consists of the speed controller and the state feedback. The effectiveness of proposed method is confirmed by the numerical simulation using a 3-DOF industrial robot model.

Recently, the size of digital content has continued to increase. In order to cope, manufacturers of digital storage media have tried to increase capacity by narrowing the track pitch of these digital storage media. In addition, recent advancements in technology have resulted in a new optical disk has a rotation speed of over 15,000 rpm. Considering all these factors, we believe that a high-precision tracking control system is needed for optical disks. Consequently, this paper proposes a new robust double feedforward control (RDFFC) system for high-precision control. The proposed system is constructed by using two error prediction-based zero phase error tracking (ZPET) control systems, and includes an error-based disturbance observer (EDOB) that uses notch filter to suppress non-periodic disturbances. The proposed control system is designed for DDU-1000 for DVD. The experimental results confirm that our proposed system is practicable and effective.

This paper proposes a new numerical simulation model of angular transmission error of strain wave gear, and designs a robust speed control system for the robot arm with this angular transmission error. The proposed numerical simulation model can confirm the vibration of the robot arm caused by this angular transmission error. It is very difficult for the conventional control system using both a PI controller and a state feedback to suppress the vibration of the robot arm completely. The proposed robust speed control system, which is a two-degrees-of-freedom control system based on disturbance observer, can suppress the arm vibration. The numerical simulation results show the proposed system well regulates the motor speed and suppresses the vibration of load speed.

In order to get a high performance and a high accuracy for servo system in several industrial applications, a servo motor system requires a realization of robust control for wide speed range. The conventional robust control system based on disturbance observer can easily design a reference response and a disturbance rejection response, but it often does not consider a robust stable condition. In order to overcome this problem, this paper proposes a new two-degrees-of-freedom control system based on disturbance observer and coprime factorization. The proposed two-degrees-of-freedom control system considers a robust stable condition and a disturbance rejection response systematically. If the frequency band of disturbance rejection is narrow, the proposed system satisfies the robust stability conditionIn this paper, the robust speed servo system of DC servo motor is constructed by the proposed two-degrees-of-freedom control system. The experimental results show that the proposed speed servo system well regulates a motor speed robustly for wide speed range, in comparison with the conventional robust speed servo systems.

Pickup systems for optical disks operate in the horizontal and vertical directions for tracking and focusing, respectively. Conventional optical disk control systems are designed for each operated direction. On the other hand, in this paper, we consider the operation trajectory to implement a method for concurrent control of focusing and tracking of optical disks. This paper proposes a two-dimensional feedforward control system. The proposed control system consists of a feedforward controller and a two-dimensional feedforward compensator. The error vector is a combination of the focusing error and the tracking error of the compensator. The feedforward controller based on a zero phase error tracking control (ZPETC) regulates the error vector. The experimental results show the effectiveness of the proposed control system.

Recently, the size of digital content has continued to increase; therefore digital storage media have been required to increase capacity by narrowing the track pitch and the gap length between the optical head and the disk. On the other hand, anew optical disk has achieved a rotation speed of over 15,000 rpm. To meet these demands, several control systems for optical disks are proposed to achieve high-precision tracking control. In this paper, a high-precision focusing control system is proposed. The proposed control system consists of a feedback controller and a feedforward controller. The feedback controller design is based on a high-gain servo controller (HGSC). The feedforward controller design is based on a zero phase error tracking (ZPET) controller and an additional loop for suppressing multi-harmonic disturbances. The experimental results show the proposed control system has a fine focusing performance against fundamental periodic disturbances and high-order disturbances.

This paper proposes a new high-precision feedforward tracking control system in single-rate sampling. The experimental results confirm that the proposed system well suppresses the tracking error on condition of disk rotation speed 7200[rpm] DVD. Therefore, the proposed system realizes high-precision tracking control.

This paper proposes a new motion control method for industrial robots. It is important to regulate the motion of robot on condition of high-speed and high-accuracy for industrial robots. However, industrial robots often occur vibration phenomenon which is caused by the resonant frequency and nonlinear interference force from various joints of the robot. A zero-phase notch filter is very useful for suppressing the resonant phenomenon. However, as the design method of zero-phase notch filter is more difficult than that of the zero-phase low-pass filter, the high-performance zero-phase notch filter cannot be realized in motion control field. In order to overcome this problem, this paper proposes a new design method of the zero-phase notch filter which has no phase delay for fast robot motion control reference. Using the proposed method, this paper achieves fast and accurate robot motion control without vibration phenomenon and overshoot. The experimental results confirm that the control system based on the proposed method well regulates fast accurate path tracking control smoothly and rapidly.

This paper proposes the modified zero phase error tracking-feedforward control (ZPETm-FFC) system. The ZPETm-FFC system is higher-speed and more precise control system than the conventional control systems which are the feedback controller of phase lead-lag filters or the ZPET-FF control (ZPET-FFC) system. Numerical simulations show the performances of ZPET-FFC system in detail of practical conditions, and the more effective control method is proposed. Experimental results show the servo performances of the proposed control system on an optical disk drive at high-speed of 11000 rpm, which is equal to Blu-ray disc system of 13.6 X speed. These results indicate that the proposed ZPETm-FFC system realizes higher-speed and more precise tracking servo performance than the conventional methods.

The optical disk system is widely used as a data storage system. The tracking control system of optical disk system requires a high precision and robustness against periodic disturbance and sudden disturbance. Therefore, it is difficult for only conventional feedback control system to realize the high-precision and robust tracking control system. This paper proposes high performance tracking control system for optical disk which is a perfect tracking control based on a plant system and zero phase low pass filter. The experimental results point out that the proposed system realizes the high precision tracking control on condition of the disk rotation speed 7,200[rpm], which is equal to conventional HDD disk speed.

The tracking control system of next-generation optical disk system requires a high precision and robustness against periodic disturbance and sudden disturbance. The next-generation optical disk system will have the high rotational speed such as more than 10000 [rpm]. Therefore, it is difficult for only conventional feedback control system to realize the high-precision and robust tracking control system. This paper proposes a single rate fine perfect tracking controller which is a new high performance tracking control system based on perfect tracking controller using only plant system model. Usually, perfect tracking controller is the multi rate controller. However, tracking control system of optical system has a rich input information, because the tracking error signal is analog signal. Therefore, this paper proposes a perfect tracking controller who operates by a single rate. The numerical simulation results point out that the proposed system realizes the high precision tracking control on condition of the disk rotation speed 8000 [rpm], which is equal to CD system of 40 X speed.

Industrial robots are always requested to realize a fast position control and keep a robot safety on external force. In order to realize a fast position control, we have already proposed both the dynamic internal torque compensation of its motion reference and the robust continuous path tracking control with vibration suppression control. For the purpose of keeping the robot safety on external force, it is important to detect the external force which is separated from the dynamic internal torque on its motion control. Hence, this paper proposes a new fast position control considering robot safety based on dual dynamic torque compensation for industrial robots. The proposed control system realizes both the robust fast position control of its motion reference and the impedance control for robot safety. The paper applies the proposed method to the motion control of tested industrial robot manipulator and confirms the validity by the numerical simulation and experimental results.

In next generation optical disk system, the disk rotation speed becomes nearly equal to 10000[rpm]. Since the optical disk systems have a radial run-out, its phenomenon becomes the periodic disturbance whose bandwidth depends on the disk rotational speed. Hence, the tracking control system of next generation optical disk recording system should have the robust precision control against the high speed periodic disturbance whose rotational speed is nearly equal to 10000[rpm]. Moreover, this tracking servo system should have and the wide bandwidth. For this purpose, the feedforward controllers such as Zero Error Phase Tracking (ZPET) control and Perfect Tracking Control (PTC), have been proposed the tracking control for the mass strage system. However, for the next generation optical disk system, it is sometimes diffcult to realize the feedforward controller for suppression of high speed periodic disturbance. This paper proposes the structure of feedforward controller based on the prediction of tracking error. Moreover, the total control structure realizes the proposed feedforward controller with a new robust feedback control system. The experiment results point out that the proposed system well regulates the high precision tracking control on condition of the disk rotation speed 8000[rpm], which is equal to the rotation speed of 40 X speed on CD system.

In next generation optical disc system, the disc rotation speed becomes nearly equal to 10000[rpm]. Therefore, the tracking servo system for next generation optical disc system must have the high precision performance and the wide bandwidth. However, since the optical disc systems have a radial run-out, its phenomenon becomes the periodic disturbance whose bandwidth depends on the disc rotational speed. Hence, the tracking servo system of the next generation optical disc system should have the robust and high precision control against the high speed periodic disturbance whose rotational speed is nearly equal to 10000[rpm]. This paper proposes a new structure of robust tracking servo system, which suppresses the high speed periodic disturbance whose rotational speed is nearly equal to 10000[rpm]. The experiment results point out that the proposed system well regulates the high precision tracking servo control on condition of the disc rotation speed 8000[rpm], which is equal to CD system of 40 X speed.