Commercial Motion Control Research Articles

Tracking of cogging stiffness using the multi-bin SDFT

Due to the high power density and wide speed range, a permanent magnet synchronous motor (PMSM) is commonly used in industry. Efficient production requires optimized motion control of the mechanism driven by the PMSM. Unfortunately, designing the controller is usually based on a model of the mechanism without including parameters originating from the motor. Cogging stiffness originates from the magnetic forces between rotor magnets and stator teeth and is one of these forgotten parameters. The performance is sub-optimal when this stiffness is not considered during control design. The stiffness also changes over time due to changing load conditions such as temperature. Aiming for optimized motion control of high-speed mechanisms, this article proposes to expand the classic motion controller with an on-line stiffness tracker. The tracker is based on the sliding discrete Fourier transform (SDFT). The tracking technique is conceptually analyzed and experimentally validated on a PMSM-driven rod. The classic Welch technique having an update time of at least 100 s is used as a benchmark. With similar accuracy and a much faster update time of 1.25 ms, the stiffness is tracked on-line using SDFT. The developed stiffness tracker is implemented on the provided commercial motion controller, proving its computational efficiency.

Experimental Assessment of Fractional-Order PDD1/2 Control of a Brushless DC Motor with Inertial Load

The application of Fractional Calculus to control mechatronic devices is a promising research area. The most common approach to Fractional-Order (FO) control design is the PIλDµ scheme, which adopts integrals and derivatives of non-integer order λ and µ. A different possible approach is to add FO terms to the PID control, instead of replacing integer order terms; for example, in the PDD1/2 scheme, the half-derivative term is added to the classical PD. In the present paper, by mainly focusing on the transitory behaviour, a comparison among PD, PDµ, and PDD1/2 control schemes is carried out, with reference to a real-world mechatronic implementation: a position-controlled rotor actuated by a DC brushless motor. While using a general non-dimensional approach, the three control schemes are first compared by continuous-time simulations, and tuning criteria are outlined. Afterwards, the effects of the discrete-time digital implementation of the controllers are investigated by both simulation and experimental tests. The results show how PDD1/2 is an effective and almost cost-free solution for improving the trajectory-tracking performance in position control of mechatronic devices, with limited computational burden and, consequently, easily implementable on most commercial motion control drives.

Software-Based Integral Product Architecture for Modular Motion Control System of a RFC Linear Motor Motion Stage: Model-Based DOB for Residual Vibration Suppression

Together with strong ICT technology and concept of smart factory, motion control system is driving innovation and increased productivity across the industrial landscape. Thus, motion control systems built with modular approach has ever-longer lists of demands for performance improvement. This paper presents software-based integral product architecture for the modular motion control system of a RFC linear motor motion stage: a model-based DOB for residual vibration suppression. First, the modular motion control system of a linear motor motion stage with air bearing is introduced and its digital twin or multi-rate simulation model is verified with experiments. Then, software-based integral product approach or a model-based DOB is applied to improve the performances of the linear motor stage and its feasibility is confirmed based on the simulation model. Auxiliary software to implement the model-based DOB into a commercial motion control are developed including excitation, DOB user code and data import. Finally, the model-based DOB is shown to improve both motion jitter and settling time of the motion stage through experiments. Precisely, 93% of the following error and 84% the settling time of ± 0.5 μm window are improved.

Servo X-Y biaxial feed system of flux switching permanent magnet linear motor.

As both magnets and coils are arranged in the motor primary, a short primary long secondary flux switching permanent magnet linear motor (FSPMLM) is favorable to construct a feed system, especially for long distance, multi-axis applications. A novel FSPMLM with a complementary primary module and end-PM topology is proposed to directly drive a biaxial feed system, and the whole structure is presented. To consider the influence of temperature raise on motor performance, magnetic-thermal coupling finite element analysis is employed, and then, the motor dimensions are optimized by the response surface method. With the same 500 N rated force and 1.5 m/s rated speed of the two FSPMLMs, the biaxial prototype is fabricated. Considering the two-axis synchronization, the control system is constructed by using a commercial motion controller and servo drivers. Monoaxial and biaxial feeding experiments are carried out simultaneously. Both X and Y axes exhibit sufficient force capability for well dynamic response, and the positioning error is less than 0.14 mm. Biaxial diamond and circular trajectories are conducted, and the contour errors are less than 0.88 mm. It can be seen that the proposed FSPMLM feed system is featured with favorable performance and competitiveness for applying in various industrial applications.

체감형 배드민턴 게임을 위한 스윙 인식과 셔틀콕 궤적 계산 방법

ABSTRACT Recently there have been many interests on tangible sport games that can recognize the motions of players. In this paper, we propose essential technologies required for tangible games, which are methods for swing motion recognition and the calculation of shuttle cock's trajectory. When a user carries out a badminton swing while holding a smartphone with his hand, the motion signal generated by smartphone-embedded acceleration sensors is transformed into a feature vector through a Daubechies filter, and then its swing type is recognized using a k-NN based method. The method for swing motion presented herein provides an advantage in a way that a player can enjoy tangible games without purchasing a commercial motion controller. Since a badminton shuttle cock has a particular flight trajectory due to the nature of its shape, it is not easy to calculate the trajectory of the shuttle cock using simple physics rules about force and velocity. In this paper, we propose a method for calculating the flight trajectory of a badminton shuttle cock in which the wind effect is considered.

A CNC program module based on polar coordinate system

Polar coordinate system is more effective for rotational axes than Cartesian coordinate one. But most commercial motion control cards do not support the polar coordinate, so this paper presents a program module based on polar coordinate system, which can be integrated into computer numeric control (CNC) controller based on motion control cards. To access the module, a special G code is developed. The module is implemented on a custom-made CNC controller and used to machine a class of watch parts. The experimental results show that the module is effective and easy to use.

FPGA를 이용한 범용 모션 컨트롤러의 개발

We have developed a general purpose motion controller using an FPGA(Field Programmable Gate Array). The multi-PID controllers and GUI are implemented as a system-on-chip for multi-axis motion control. Comparing with the commercial motion controller LM 629, since it has multi-independent PID controllers, we have several advantages such as space effectiveness, low cost and lower power consumption. In order to test the performance of the proposed controller, motion of the robot hand is controlled. The robot hand has three fingers with 2 joints each. Finger movements show that tracking was very effective. Another experiment of balancing an inverted pendulum on a cart has been conducted to show the generality of the proposed FPGA PID controller. The controller has well maintained the balance of the pendulum.

Torque and current control of high-speed motion control systems with sinusoidal-PMAC motors

Describes a torque- and current-control application to a commercial motion-control system with sinusoidal permanent magnet ac (PMAC) motors. The control approach is based on maximization of torque-per-amp ratio. The proposed torque controller, in the form of torque feedforward plus proportional-integral (PI)-type torque feedback, utilizes the feedback of nominal torque signal only, a signal that can be readily calculated, online. No torque sensor is required. Through proper design of the desired nominal torque with adaptive control, the proposed torque controller can overcome disturbances due to torque estimation error and model uncertainties. A discrete-time approach is developed for inner-current loop control design. The inner-loop control gains, which are hard to obtain through manual tuning in practice, are determined by a dynamic model-based calculation methodology. Experimental evaluation on a commercial motion control system demonstrates the validity of the proposed approach in high-speed motions.