Used Stepper: 17HM19-2004S
Driver Voltage: 37V
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.
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.