Encoder for linear motor, linear motor and position detection method thereof

Abstract

The invention relates to an encoder for a linear motor, the linear motor and a position detection method of the linear motor. The encoder is characterized by comprising at least one magnetoresistive sensor, a first Hall switch sensor, a second Hall switch sensor, a signal acquisition and processing unit and an operation unit, wherein the distance between the first Hall switch sensor and the secondHall switch sensor is S*(2*n+1) / 4, and the first Hall switch sensor and the second Hall switch sensor generate two orthogonal pulse signals with the phase difference of 90 degrees respectively; the signal acquisition and processing unit is used for processing the two groups of voltage signals acquired by the magnetoresistive sensor to obtain an angle value changing along with the primary position; and the operation unit is used for calculating primary absolute position information according to the first orthogonal pulse signal, the second orthogonal pulse signal and the angle value obtained by the signal acquisition and processing unit. Compared with the prior art, the encoder has the advantages that the primary absolute position information is obtained by arranging the magnetoresistive sensor and the two Hall switch sensors, and the magnetoresistive sensor and the Hall switch sensors have low requirements on the mounting environment and the magnetic field precision of the secondary magnetic steel, so that the popularization and application range is wide.

Description

technical field [0001] The invention relates to an encoder, in particular to an encoder for a linear motor, a linear motor using the encoder and a position detection method thereof. Background technique [0002] Currently, there are mainly two types of encoders used in linear motors: optical linear encoders and magnetic induction linear encoders. The optical linear encoder needs to install a linear grating on the motor body, and then read the optical signal through the encoder's read head and convert it into position information output; the magnetic encoder needs to install a linear magnetic grating on the motor body, and then pass the encoder's The read head reads the magnetic signal and converts it into position information output. No matter what type of encoder, it is necessary to additionally install a scale (grating or magnetic grid) on the motor body, which has disadvantages such as high cost, complicated installation, and difficult control of the size of the error. ...

AI Technical Summary

Problems solved by technology

No matter what type of encoder, it is necessary to additionally install a scale (grating or magnetic grid) on the motor body, which has disadvantages such as high cost, complicated installation, and difficult to control the size of the error.

[0003] In addition, the grating is easily affected by the environment such as oil pollution and dust, so it is not suitable for application under harsh working conditions

The anti-pollution ability of the magnetic grid is relatively good, but the magnetic grid is easily magnetized by the external magnetic field, especially for small linear motors, the magnetic scale should be installed away from the magnetic steel on the secondary side inside the motor, otherwise it will be magnetized and cause the encoder to fail

[0004] In addition, generally linear gratings or magnetic gratings are incrementally engraved and cannot provide absolute positions. Therefore, when applied to linear motors, they cannot provide primary phase information in the motor. When the linear motor is powered on for the first time, there will be primary Relatively large position movement is not allowed in many applications. In order to overcome this shortcoming, some motors are additionally equipped with a Hall phase sensor to sense the phase of the primary motor, which not only increases the complexity of wiring but also increases the cost.

[0005] In order to solve the shortcomings of linear encoders such as complex installation, high cost, susceptibility to pollution, and the influence of magnetic fields, a Chinese patent with publication number CN 106849520 A discloses a magnetic track encoder for linear motors, which includes a housing, and is installed in the housing There is a PCB board, wherein, the PCB board is provided with a Hall sampling circuit for collecting the magnetic field signal generated by the primary during motion, and converting the magnetic field signal into two voltage signals with a phase difference of 90°; A subdivision circuit for subdividing the two-way voltage signals into preset multiples to obtain two-way orthogonal encoder signals; a differential signal conversion circuit for converting the two-way orthogonal encoder signals into differential signals, through the Huo The sampling circuit collects the magnetic field signal and converts it into a voltage signal. After subsequent subdivision and differential signal conversion processing, accurate position data can be obtained.

In this structure, the Hall sampling circuit adopts the first Hall sensor and the second Hall sensor which can convert the magnetic field signal into a sine voltage signal and a cosine voltage signal respectively, and the first Hall sensor and the second Hall sensor must adopt linear The Hall sensor can obtain the primary position data in the subsequent processing; however, the linear Hall sensor must work in the linear range and has relatively strict requirements on the range of magnetic field strength. Therefore, the use environment of the encoder is limited. Certain restrictions, and in order to avoid being affected, it must be equipped with a shielding case. In addition, after the encoder is installed, the requirements for the magnetic field consistency of the multiple magnets arranged in the secondary are also high, otherwise its accuracy will be greatly affected; However, in many cases, due to the magnetic field magnetization accuracy of the secondary magnetic steel of the motor, there is often a certain physical deviation, and at the same time, there will be some large physical errors when the magnetic steel is installed. In these cases, the absolute positioning of the encoder will be greatly reduced. precision

However, in some occasions that require high precision (printing, machine tools, semiconductor industries, etc.), it is necessary to compensate the motor encoder for full-stroke accuracy, and the above encoders cannot meet the requirements.

Moreover, the above-mentioned encoder does not output the phase information obtained by the Hall sensor. The linear motor using this encoder will still have a relatively large primary position shift when it is first powered on to find the phase. This is not true in many applications. Allowed

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