Low-resolution coder position calculating method for electric forklift

Abstract

The invention discloses a low-resolution coder position calculating method for an electric forklift. The method includes following steps: step 1, setting a fixed calculating period, measuring pulse number in each calculating period, measuring time between a last pulse time moment in the calculation period and a finishing time moment of the calculation period, and acquiring a rotating angle of a rotor in the current calculating period according to a measuring result through an algorithm, namely actual measuring position of the rotor; step 2, adopting a phase-locked loop method, and calculating rotating speed according to the rotating angle of the rotor in each calculating period through a phase-locked loop adjuster. Deviation compensation is performed on the actual measuring position according to orthogonal error information, so that errors caused by signal non-orthogonality of an incremental coder are reduced, accurate rotor position information is acquired finally, position measuring deviation can be reduced, and speed calculation errors are reduced; the algorithm is simple and uncomplicated to realize, hardware design does not need to be changed, and control performance of the forklift is improved.

Description

technical field [0001] The invention relates to the technical field of electric forklifts, in particular to a method for calculating positions of low-resolution encoders used in electric forklifts. Background technique [0002] Vector control strategies are usually used in electric forklifts to achieve high-performance induction motor control. At this time, an external position sensor is required to provide real-time rotor position. Due to the constraints of cost, working environment and reliability, low-cost magnetoresistive encoders are usually used. At this time, not only the resolution is low, but the orthogonality is poor. [0003] The angle measurement sensor of the electric forklift motor is usually an incremental encoder. Due to the cost and reliability requirements, the resolution of the encoder is very low, and the signal orthogonality is poor. How to extract effective position information and speed information from this signal is one of the difficulties in forkli...

AI Technical Summary

Problems solved by technology

Due to the constraints of cost, working environment and reliability, low-cost magnetoresistive encoders are usually used, at this time not only the resolution is low, but the orthogonality is poor

[0003] Electric forklift motor angle measurement sensors are usually incremental encoders, due to cost and reliability requirements, the resolution of the encoder is very low, and the signal orthogonality is poor

How to extract effective position information and speed information from this signal is one of the difficulties in forklift motor control. The traditional speed calculation method is based on the number of pulses within a certain period of time. The accuracy of position and speed information calculated by the traditional calculation method is poor. However, the low resolution and orthogonality of the encoder will cause a large position measurement error, and the position error will affect the decoupling accuracy of the vector control variable.

At the same time, the speed is also calculated from the position measurement value, so the speed calculation result is not accurate enough

The traditional method adopts digital filter or adopts a longer calculation period, at this time, the calculation accuracy of the speed will increase, but the real-time performance is poor, which makes the dynamic response characteristics of the speed poor

Position difference and speed error will reduce motor torque and speed control performance, causing vehicle comfort and vehicle safety hazards

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