KR100739349B1 - Initial location measurement method of the linear hybrid stepping motor - Google Patents

Abstract

A method for estimating an initial position of a linear hybrid stepping motor(LHSM) is provided to perform accurate position control not only at closed loop control but also at open loop control, by enabling initial start and accurate torque generation of the LHSM. In a method for estimating an initial position of a linear hybrid stepping motor(LHSM), a positive thrust curve is formed by applying a DC to the LHSM. The initial position is estimated by DC current control in the initial driving by estimating initial load, after judging absolute position where the positive thrust and the initial load meet. Position error generated in position control is removed by controlling the LHSM by an open loop control method attached with a speed and position sensor.

Description

Initial location measurement method of the Linear Hybrid Stepping Motor

1 is an overall configuration diagram of an LHSM constructed in accordance with a preferred embodiment of the present invention.

The present invention relates to a linear hybrid stepping motor (LHSM) configured to generate thrust by using a permanent magnet, and in particular, it is possible to estimate the initial position by using the thrust curve of the LHSM. It is intended to implement a system that enables smooth start and accurate torque generation at start-up, and it is a closed loop that complements the existing system that makes it impossible to attach expensive sensors for general initial position detection due to the finely formed pitch interval. In addition to the method, it is configured to enable accurate position control in the open loop method.

Industrial equipment for linear motion, which is used in industrial fields today, is mainly used by a dual-drive system, such as a ball screw, which combines a rotary motor with a mechanical addition device that converts the rotational motion of the motor into linear motion. However, the system configuration is complicated and high precision is required for machining, and there are many problems in terms of cost and precision due to limitations in high-speed response, durability and precise position control. In particular, the limit is prominent in the case of a drive source of a precision small system.

The interest of linear motors is increasing due to the limitations of cost and control accuracy which are pointed out as problems in most systems using rotary motors. Such linear motors are mechanical linear motion converters such as cranks, chems, gears and chains. It is ideal for linear motion systems because it can generate linear propulsion directly by the motor itself without the same power converter.

In general, a linear motor can be classified into a linear synchronous motor, a linear induction motor, a linear direct current motor, and a linear stepping motor. In particular, a linear synchronous motor is mainly used in a linear servo system requiring precision position control. It has been pointed out that the synchronous motor is structurally complicated and the unit cost increases because a permanent magnet must be attached to each pitch of the stator. Therefore, in recent years, by using less permanent magnets compared to linear synchronous motors, the structure is simpler and can be produced at a lower price. Also, inexpensive open loop control is basically possible, and when used for positioning control, other types of linear motors are used. Compared to the situation, the linear stepping motor has been applied to various devices.

The linear stepping motor has a tooth in the form of a gear in the mover, the moving speed is proportional to the frequency of a given input signal, and the moving distance is a motor moving in synchronization with the input signal. Therefore, it is classified into three types: permanent magnet (PM), variable reluctance (VR), and hybrid (hybrid).

Briefly looking at the three forms described above are as follows. The variable reluctance type has a rotor (rotor) made of soft iron or stratified steel, and is rotated by the electromagnetic force produced by the toothed rotor and stator windings. Since it does not occur anywhere, the holding torque becomes zero, and the stepping motor has an advantage of small inertia of the rotor and favorable for high speed response. The permanent magnet stepping motor is a motor that uses a permanent magnet as a rotor and rotates by the magnetic force generated in the stator winding.The permanent magnet uses a permanent magnet and has a holding torque even in the absence of permanent magnets. Step angles are categorized according to the type, and 90 ° and 45 ° motors having large step angles generally use alnico magnets and ferrite magnets for motors such as 18 °, 15 ° 11.25 ° and 7.5 °.

In addition, the hybrid stepping motor LHSM to which the present invention is applied is a hybrid stepping motor that generates thrust using a permanent magnet and an electromagnet at the same time. It is possible to drive bipolar and has high utilization rate and efficiency of winding, and it is simple in structure and can be miniaturized, and it has a feature of greater thrust per unit input than other linear motors. In addition, due to the characteristics that vibration does not occur at the stop, it has recently been widely applied in industrial processes and automation equipment that requires a stop thrust.

On the other hand, the LHSM requires a proper control method for smooth start and accurate servo operation at start-up, and to obtain energy saving and high efficiency. In order to obtain these results, it is essential to find out exact position information of the mover. . Therefore, in the related art, an expensive sense is inevitably attached in order to estimate accurate positional information of the mover. However, in the current industry, low cost and compact size are required, and thus, expensive sensors are generally not attached. Permanent magnet linear motors require expensive stimulation sensors, but they are also susceptible to dust, heat, noise, and mechanical vibrations, which can lead to misreading situations and provide sufficient thrust if the exact location of the stimulation sensors is not known. This can cause system instability or cause the motor to move in the wrong direction at start-up, resulting in control instability.

Recently, methods for estimating the initial position of a rotor of a permanent magnet synchronous motor have been studied, and these estimation methods are related to a rotating device such as an embedded permanent magnet synchronous motor and a surface mounted permanent magnet synchronous motor. It is not possible to directly apply LHSM with tight pitch spacing.

In order to solve the above problems, the present invention provides a method for determining accurate position information of the rotor by DC current injection to enable smooth initial start-up and accurate torque generation of the LHSM. The purpose is to configure accurate position control in the control.

The features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings, in which the terms or words used in the present specification and claims are best described by the inventor in the best way. Based on the principle that the concept of the term can be properly defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

Typical hybrid stepping motors (LHSMs) require 200 schritt per revolution and are used in many applications where position movement is necessary because it is easy and inexpensive to set the exact position without a separate measuring system or positioner. It is strong, semi-permanent, and has a large torque force at standstill or at low rotational speeds.

The present invention relates to an LHSM configured to generate a thrust using a permanent magnet, which allows the initial position to be estimated by using the thrust curve of the LHSM, thereby enabling smooth starting and accurate torque generation during initial startup. We want to implement the system.

Hereinafter, the configuration and means for the LHSM of the present invention will be described in detail with reference to the accompanying drawings and a plurality of experimental data.

Figure 1 shows the overall structure of the two-phase LHSM to which the present invention is applied, the number of poles of the proposed structure is 12 poles, it is made of a combination of mono-filler winding and bi-filler winding. This is to match the two LHSMs to obtain the offset of the thrust ripple. The structure has a phase difference of ± 90 ° and ± 45 ° of the magnetic force due to the current generated at each pole, and the currents of the A and B phases generated at each pole. Has a 90 ° phase difference. In addition, the mechanical phase difference between the windings of the moving poles is characterized in that 45 °, 90 °, -45 °, 180 ° from left to right.

The LHSM proposed in the present invention has a pitch interval of 1 mm corresponding to 360 ° in the rotary motor. Therefore, as it becomes impossible to attach a sensor for detecting a general initial position at a minute pitch interval, the present invention estimates the initial position using the thrust curve of the LHSM. The following data is a graph of the thrust curves based on experimental values.

                    <Graph 1>

                    <Graph 2>

The above graph 1 shows the thrust force that forms the movement of the mover when the DC current is excited on the phase A, and the graph 2 shows the thrust force that forms the movement of the mover when the DC current is excited on the A and B phases, These graphs are graphed to easily recognize the moving direction of the mover according to the thrust curve generated when the DC current is excited on the A and B phases. Here, it can be seen that when the thrust occurs, the mover moves to a stable point forming a balance of forces.

Disregarding the reluctance thrust of the modeled LHSM, the generated thrust is as follows.

로 전류를 인가하면 다음과 같은 정추력식을 얻을 수 있다.if,

When the current is applied, the following thrust equation can be obtained.

의 평형점은 다음과 같다.In graph 3, which will be described later,

The equilibrium point of is

If there is an initial load, the equilibrium point moves as shown in graph 4. Therefore, since the point where the initial load meets the thrust force becomes the absolute position, it means that the initial position can be found by estimating the initial load.

                    <Graph 3>

                    <Graph 4>

The graph 3 shows the equilibrium point and the thrust force according to the excitation of the phase A at no load, while the graph 4 shows the equilibrium point and the thrust according to the excitation of the phase A when there is an initial load as opposed to 3.

로 입력하면 다음과 같은 정추력을 계산할 수 있다.Current

If you enter, you can calculate the following thrust force.

On the other hand, the equilibrium point at no load is as follows.

Now, look at with respect to the estimation of the initial position by using the thrust according to the present invention.

                    <Graph 5>

                    <Graph 6>

의 평형점을 이용한 초기추정 원리를 도시하였다. 먼저, A상을 여자시켜

를 발생시키면 이동자는 초기위치

에서

로 이동한다. 그리고, 이 때

를 발생시키면

에서

로 이동한다. 삼각함수 관계를 이용하여

를 계산하면 다음과 같다.Graph 5 shows the equilibrium point and the thrust force according to the excitation of the A, B phase at no load, Figure 6 shows the principle of the initial position estimation according to the excitation of the phase A and A, B phase, in particular Figure 6 Thrust

The principle of initial estimation using the equilibrium point of is shown. First, let's make A woman

Move the initial position

in

Go to. And at this time

When you generate

in

Go to. Using trigonometric relations

The calculation is as follows.

는 정격전류이며,

는 엔코더로부터 검출할 수 있는 값이다.here,

Is rated current,

Is a value that can be detected from the encoder.

을 구하면 다음과 같다.The three equations above

Is obtained as follows.

에 대입하면

를 계산할 수 있으며, 이것으로 초기위치를 알 수 있게 된다.Stomach expression

Substituting in

Can be calculated, and the initial position can be known.

                                   TABLE 1

Table 1 above is a comparison of the estimated initial position according to the load fluctuation, and shows the estimation result of the initial position when the load is changed to 0 ~ 40N, it can be seen that the estimated error is very accurate to ± 5 ° . Therefore, the initial estimation technique proposed in the present invention can show a very accurate initial position estimation capability by simple current control without a separate device. It is possible to eliminate the position error caused by position control by attaching a low-speed speed and position sensor even in the normal closed loop control method that requires the speed and position sensor as well as the open loop control method that does not use the speed and position sensor. There are features that can be.

Embodiment described above is configured to help the understanding of the present invention, it is only one embodiment that can be applied to the present invention, and the scope of the present invention is not limited to the above-described embodiment.

According to the present invention implemented in the above manner, it is possible to realize a very accurate initial position estimation ability by the simple direct current control of the initial operation without a separate device to generate accurate torque, open and close loop which is a conventional control method The control method also has the effect of enabling accurate position control.

Claims (2)

In the method for estimating the initial position of the linear hybrid stepping motor (LHSM) consisting of a two-phase structure, Linear hybrid stepping that allows direct estimation of initial position by DC current control at the beginning of operation by applying direct current to the LHSM to form a thrust curve, grasping the absolute position where the forward thrust and the initial load meet, and then estimating the initial load. How to estimate the initial position of the motor. The method of claim 1, An initial position estimation method of a linear hybrid stepping motor characterized in that the LHSM is controlled to remove the position error generated during the position control by controlling the low-speed speed and position sensor attached to the open loop control method.

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