Masaki Sazawa

Sensorless Force Control for Injection Molding Machine Using Reaction Torque Observer Considering Torsion Phenomenon

Recently, many plastic products have been produced and used. These plastic products are mostly manufactured using injection molding machines. The quality of plastic products depends on the injection force. Therefore, it is important to develop a fine force-control system. Generally, in force-control systems, the force information from the environment is detected by a force sensor. However, control systems using force sensors present problems related to signal noise, sensor cost, narrow bandwidth, and other factors. To overcome these problems, this paper presents a proposal for a new sensorless force-control method using a reaction torque observer. The injection molding machine, which uses a ball screw, has a resonance frequency that is affected by the torsion phenomenon. This new reaction torque observer considers the torsion phenomenon and friction phenomena.

High efficient speed control of parallel-connected induction motors with unbalanced load condition using one inverter

Recently, the parallel speed control of two induction motors, which uses only one inverter, has been proposed by the vector control method. However, the conventional control method does not consider both the efficiency of the motor control and condition of different load torque to each induction motor (IM). This paper proposes a new high efficient parallel speed control method, which calculations the optimal voltage and frequency value based on non-linear programming method, even when two induction motors on condition different load torque. The non-linear programming method requires the information on load torque and speed reference. Each load torque is estimated by disturbance observer with current simulator and flux simulator. The IM driven system requests only speed sensor using rotary encoder. Hence, it has no current sensor and no voltage sensor. The experimental results point out that both induction motors keep the near same speed control performance with high efficiency in the steady state and the transient state, on condition of different load torque.

High efficient parallel-connected induction motor speed control with unbalanced load condition using one inverter

Recently, the parallel speed control of two induction motors, which uses only one inverter, has been proposed by the vector control method. However, the conventional control method does not consider both the efficiency of the motor control and the condition of different load torque to each induction motor (IM). This paper proposes a new high efficient parallel speed control method of two induction motors on condition of different load torque, which is based on non-linear programming method. The non-linear programming method requires the information on load torque and speed reference. Each load torque is estimated by disturbance observer and current simulator. The IM drive system requests only speed sensor such as rotary encoder. Hence, it has no current sensor and no voltage sensor. Moreover, this paper discusses the condition of low-resolution rotary encoder, such as 60pulse/rev. The numerical simulation results point out that both induction motors keep the nearly same speed control performance with high efficiency in steady state and the transient state on condition of different load torque.

Robust High Speed Position Servo System Considering Current & Voltage Limitation and Load Inertia Variation

A high speed position servo system is important for performance improvement of motion control in several industry applications. It often has the desired position reference. An industrial servo system has the limitation values based on each output of actuator and power amplifier. Hence, a high speed position servo system should keep the tracking control for the desired position reference within the limitation values. Moreover, an industrial servo system must realize the robust control against load torque and load inertia variation. An ordinary position servo system has the complicated control structure caused by the triple minor control loops. On condition of both load inertia variation and the saturation caused by current & voltage limitation, an industrial servo system sometimes has a large overshoot and an oscillated response. Therefore, for the desired quick position reference, it is difficult for a high speed position servo system to keep the robust tracking control against load inertia variation within each limitation of motor current and motor voltage. In order to overcome this problem, this paper proposes a new robust high speed position servo system considering current & voltage limitation and load inertia variation, which is based on disturbance observer. The experimental results confirm that the proposed system realizes the desired & quick & robust response keeping each limitation of speed, current and voltage on condition of both full load torque and three times load inertia variation.

FPGA-based wideband force sensing with Kalman-filter-based disturbance observer

Haptic technology has been attracting widespread attention in the fields of robotics and medicine. The bandwidth of force sensing is vital to reproduce the vivid force sensation. This paper proposes a method to enlarge the bandwidth of force sensing. In this paper, the force sensing operation is constructed by a combination of a Kalman-filter and a disturbance observer for multi-sensor. In order to achieve the high sampling rate, the control algorithm together with the force estimation function is implemented in a field programmable gate array (FPGA). The wide bandwidth of force sensing is obtained owing to the shortened sampling period by FPGA and the noise suppression by Kalman-filter. The experimental results show the viability of the proposed method.

Robust High Speed Positioning Servo System Considering Saturation of Current and Speed

A robust servo system is important for performance improvement of motion control system in several industry applications. Generally, a high speed positioning servo system consists of robust control systems with integrator, such as PI controller. The industrial servo system always has the limitation for the capacity of actuator and power amplifier. An ordinary industrial position servo system often has the saturation of motor current and motor speed. It is difficult for the high speed positioning servo system to keep the robust position control against the saturation of motor current and motor speed. Because, an ordinary position servo system has the complicated control structure with many control loops. Hence, it sometimes has the large overshoot and the oscillated response by the limitation of motor current and motor speed. In order to overcome this problem, this paper proposes a new robust high speed positioning servo system considering the saturation of torque current and motor speed. The experimental results show that the proposed robust high speed positioning servo system the quick and stable position response for the saturation of motor current and motor speed.

Perfect Tracking Control System with Prediction State Observer for Next-Generation Optical Disks

Recently, the capacity of optical disk recording systems has been increasing. Optical disk drive systems must realize high-precision tracking control. For this purpose, we previously proposed a tracking control system that is composed of both a robust feedback controller and a zero-phase-error feedforward tracking controller. The proposed feedforward tracking control system effectively suppresses the tracking error caused by track eccentricity. However, it is sometimes difficult for conventional feedforward tracking control systems to realize higher precision in their tracking control. Hence, in this paper we propose a new perfect tracking control (PTC) system with a prediction state observer for next-generation optical disks. The experimental results confirm that the proposed system suppresses the tracking error at a disk rotation speed of 8000 rpm. Therefore, the proposed system realizes high-precision tracking control.

Fine self-tuning method of both current sensor offset and electrical parameter variations for SPM motor

The servo system of a permanent magnet (PM) motor is always required to maintain fine torque and speed response. The current-control system is designed by using the electric parameters of the PM motor. However, motor parameters vary and the current sensors have offset values. When each U-phase and V-phase current sensor has an offset value, the PM motor servo system has the torque ripple and cannot accurately identify the motor parameters. In this paper, we propose a new online-estimation method for both current-sensor offsets and electrical parameters for PM motors by using a current simulator. The experimental results confirm that the proposed method accurately estimates both the U-phase and V-phase current sensor offsets, the motor resistance Ra, the motor inductance La, and carries out the fine self-tuning for the current controller of PM motor servo system.

Fine estimation & self-tuning of both current sensor offset and electrical parameter variation for PM motor

The servo system of PM motor is always required to keep the fine torque response and the fine speed response. The current controller of PM motor should have the fine current response. However, when each current sensor of U phase and V phase has the offset value, the servo system of PM motor has the torque ripple and can not accurately identify the motor parameters such as the motor resistance Ra and the motor inductance La. In order to overcome these problems, this paper proposes a new fine estimation & self-tuning of both each current sensor offset and the electrical parameters for PM motor. The proposed method is the real time algorithm using the current simulator, which is the software system of DSP. In this paper, the experimental results confirm that the proposed method well estimates each current sensor offset of U phase and V phase, the motor resistance Ra and the motor inductance La individually and accurately, and carries out the fine self-tuning for the current controller of PM motor servo system.

Self-tuning control of both current sensor offset and electrical parameter variations for PM motor

It is very important to identify the electrical parameters accurately for the servo system of PM motor, that keep the fine torque response and the fine speed response. Generally, the electrical parameters of PM motor are identified by using the motor voltage and motor current. However, current sensor often has the offset value. In this case, the servo system of PM motor has the torque ripple and can not be identified accurately the motor parameters. In order to overcome these problems, this paper proposes a new self-tuning control of both current sensor offset and electrical parameter variation for PM motor. In this paper, the experimental results and the numerical simulation resluts confirm that the proposed method well estimates each current sensor offset of U phase and V phase, the motor resistance Ra, the motor inductance La and the motor magnetic flux Φfa individually and accurately, and carries out the fine self-tuning for the current controller of PM motor servo system.