Stepper

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General Setup

Used Stepper: 17HM19-2004S

Driver Voltage: 37V

Driver: TMC2130

Max RPM reached with the motor, unloaded: 3600RPM This is the limit of the driver. It runs from the internal oscillator at 12.1MHz. Measure by giving a 9.765kHz pulse and read out register TSTEP as 0x277 (DEDGE=true).

Take One, Lifting Weights

Driver Configuration is basically the recommended default from the datasheet for a coil current of about 2A:

reg 0x6c -> 0x200100c3
reg 0x10 -> 0x00061c02
reg 0x91 -> 0x0000000a
reg 0x80 -> 0x00003144
reg 0x93 -> 0x000001f4
reg 0xf0 -> 0x000401c8

For very slow step rates stealthChop was disabled

Load Testing at 1/256 microstepping. Testing done lifting a weight by winding a rope on a cylinder with effective radius of 16.5mm.

9.5kHz 2250g
19.5kHz 2150g 
39kHz 2240g
58.5kHz 2220g
78kHz 2240g
97.5kHz 2230g
117kHz 2230g
137kHz 2130g
156kHz 2150g
195kHz 2030g 
234kHz 2050g
312kHz 2030g
468kHz 1700g
624kHz 1300g
936kHz 740g
1092kHz 556g
1400kHz 250g
1700kHz 150g


Source for torque curve from datasheet: https://www.omc-stepperonline.com/download/17HM19-2004S_Torque_Curve.pdf

Full data sheet of the motor: https://www.omc-stepperonline.com/download/17HM19-2004S.pdf

Take Two, Weight Spinning

The idea here is to measure the torque at a given RPM by testing how fast the stepper can accelerate to a higher RPM. This way the measurement is not limit to the length of a linear motion as in the previous chapter.

Lost step detection

With each round the rotor goes through a photo interruptor. Before the start of the measurement, the controller homes the rotor so that it is interrupted. It then checks at each turn if the rotor is still in the expected position.

Measurement

1. Homing 2. Accelerate from standstill to 10 RPM very slowly 3. check for lost steps 4. if no steps are lost, slow down again (to the standstill) 5. choose a higher acceleration 6. repeat with 2 until lost steps are detected 7. repeat the same cycle going from 10RPM to 20RPM 8. repeat until max speed of 3600 RPM is reached

We now have a detailed torque curve RPM vs. Ncm.

Do the same for deceleration

Repeat everything with the other set of weights.