#the4thLichuangcompetition#HyperStepper Integrated low-cost, high-speed, high-precision fully closed-loop stepper motor

* Brief introduction to the work: Stepper motors are widely used in industrial control products due to their low cost, simple control, low speed and large torque. The traditional open-loop stepper accuracy is not high, the noise, vibration, and heat are large and easy to Out of step, the speed is basically only sufficient for applications below 1000RPM. This project aims to develop a high-speed (3000RPM) and high-precision (can be used with 1um grating ruler for fully closed-loop control) and very compact (driver and stepper motor are integrated together) closed-loop stepper, and control its cost compared to ordinary The open-loop drive step is about the same, which is far lower than the finished closed-loop stepper on the market.

[Please fill in during the competition stage↓] * 1. Details of the work; HyperStepper is a low-cost, high-precision and highly integrated integrated closed-loop stepper driver. Different from the traditional closed-loop stepper that uses photoelectric encoders, HyperStepper uses Infineon's The 15-bit giant magnetoresistive encoder TLE5012 is only a SOP8 packaged chip, so the size of the driver board can be made very small and integrated with the stepper motor. Through algorithm correction, the encoder accuracy can reach less than 0.08 degrees. The closed-loop control can dynamically adjust the motor's drive current according to the load, so that there will be no shortcomings of ordinary open-loop steppers such as loud noise, high heat and vibration. The motor position is measured in real time through the encoder, and the motor position can be positioned at will using FOC vector control, completely solving the problem of common open-loop step out of step. If you need to purchase, you can visit my Taobao store: https://item.taobao.com/item.htm?spm=a230r.1.14.1.13e8ba58s1vPDi&id=595204678303&ns=1&abbucket=8#detail . Welcome to join the QQ group to discuss technical issues. No.: 1001482975

Closed-loop step parameters: Main control chip: STMicroelectronics STM32F030C8T6 Driver chip: two TB67H450FNG (maximum current 3.5A) Encoder chip: Infineon 15-bit automotive industrial grade TLE5012B High-speed optocoupler: Toshiba dual-channel TLP2168 Working voltage: 12 -36V (24V recommended) Operating current: Rated 1.3A (42 steps) 2.5A (57 steps) Maximum 3.5A Control accuracy: less than 0.08 degrees Electronic gears: 2, 4, 8, 16 (can be customized at will)

* 2. Describe the challenges faced by the work and the problems solved; In fact, many difficulties were encountered in the production project. The first one is that the magnetic encoder chip TLE5012 has a nonlinear error of more than 2 degrees. This is also the case for all magnetic encoder chips. A common problem is that the accuracy is poor compared with traditional photoelectric encoders. The solution is to calibrate based on the full-step accuracy of the stepper motor itself, because the full-step accuracy of ordinary stepper motors can reach less than 0.08 degrees. Correction The latter magnetic encoder has the same level of accuracy as the 1000-line photoelectric encoder; the second difficulty is the problem of high-speed drive of the stepper motor. The general rated operating speed of the stepper motor is basically between 600RPM-800RPM. Continue to increase the speed. The counter electromotive force of the motor coil will be saturated, causing the torque to drop significantly, and the speed will not increase. The solution is to use weak field drive, add a field weakening current to the motor d-axis, and at the same time increase the drive current of the motor q-axis, using With this method, the motor can run above 3000RPM. The third difficulty is the problem of high precision. Ordinary closed-loop stepper only performs closed-loop control on the motor. This control method can only be called semi-closed-loop control. The elasticity of the coupling, the Factors such as rod accuracy, hysteresis, synchronous belt deformation, thermal expansion and contraction, etc. will all bring additional errors. In this way, semi-closed-loop control cannot meet the requirements in some situations that require very high accuracy. The solution is to add a 1um resolution grating. The ruler is fully closed-loop controlled. Through fully closed-loop control, the accuracy can be improved to an accuracy of plus or minus 1um (grating reference).

* 3. Describe the key points involved in the hardware and software parts of the work; In terms of hardware, the main control chip is STM32F030C8T6 with a price of about 3.5 yuan and STM32F103C8T6 with a price of about 5.5 yuan. The former is used for 3D printers and other cost-sensitive and performance requirements. In low-speed applications, the latter type of microcontroller is used for high-speed and high-precision applications; the motor driver chip uses two TB67H450FNGs with a maximum drive current of 3.5A and a withstand voltage of 50V. It is more than enough to drive 42 stepper motors and can also drive 57 stepper motors. It is basically sufficient; the encoder uses Infineon's 15-bit magnetic encoder chip TLE5012B, which is automotive industry standard, and its reliability and operating temperature are higher than consumer-grade standards; the isolation optocoupler is Toshiba TLP2168 and Everlight EL357 are used to isolate the external input CLK/STEP control signal; there are two solutions for voltage stabilization chips. One is a low-cost solution that directly uses the LDO model RS3005 that can withstand 36V high voltage, and the other uses DC-DC. The step-down chip MP2456 is used in situations where power needs to be supplied to an external grating scale.

In terms of software, the programming environment uses ARM's official professional software KEIL-MDK, and cooperates with ST's official CubeMX program to directly configure the relevant pins and built-in programs of the microcontroller, which is very convenient and trouble-free; the open-loop mode is added to the control program, although closed-loop has many advantages. But the open loop is not without its merits, so even if the encoder is broken, you can still switch to the open loop mode and continue to use it; then an option program of the dial switch is added, and the dial can be used to achieve subdivision, open and closed loop, correction and other functions For convenience of use; then add the encoder automatic correction code. The principle of correction is to let the stepper motor run 1 to 2 circles in full steps in an open loop, because the stepper motors on the market now can do 5 full steps. % (0.09 degrees) or less, based on which the encoder chip can be corrected; the core code is the PID control of the position loop. The PID algorithm is the most widely used control algorithm. For its specific application in closed-loop stepping, please refer to me Open source code.

* 4. List of materials for the work; one ordinary 42/57 stepper motor (you can choose various types of stepper motors, the program compatibility is very good) + one HyperStepper closed-loop drive control board + one 5/6/8mm radial magnet +Install nylon washers, screws, etc.

  5. Upload pictures of your work; (the PCB must have the contest logo on it and take a photo and upload it, otherwise it will be deemed as giving up the competition)   6. Demonstrate your work and record it as a video for upload; (The video content must include: work introduction; function demonstration; performance test ; Close-up shot of the competition logo on the PCB, if not seen, it will be regarded as giving up the competition) Competition LOG display video, closed-loop stepping basic operation demonstration, closed-loop stepping positioning accuracy demonstration, closed- loop stepping anti-out-of-step demonstration, closed-loop stepping weak magnetic drive running at 3500RPM high-speed demonstration of closed-loop stepping Demonstration of fully closed-loop control with magnetic grid

7. Open source documents Please see the attachment for details of open source software, hardware and BOM!