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# Stepper motor |
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## Motor model |
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Two detail steps ago we already looked in to stepper motors. |
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I implemented a model that I found on a [Github repository](https://github.com/SuYouge/Stepper-motor-modeling). |
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Sy Youge build a model of a stepper motor with a good explaination. |
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I could easily implement this. |
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I expended his bondgraph model with a phase controller. |
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I only have to put in the desired angle. However, this phase controller does not have any limiting. |
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Therefore, some control in required to make sure the physical part of the motor can keep up with the electrical rotation. |
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## Motor Control |
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This control is a seperate block. |
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There are two limitations to the controller. |
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First it has a limited speed, second it has a limited torque. |
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If you exceed this speed or torque the motor will stop operating. |
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The torque requires a good feed-forward model of the dynamic system. |
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However, I can just assume the max moment of inertia and then convert the torque in to a maximum acceleration. |
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This was the easiest option. |
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The result is that I have a setpoint for the angle. This is the setpoint for the first PD controller. |
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This is not a PID as the design of the stepper already solves the steady state error that would have been caused by gravity. |
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The first PD will then output the desired velocity. We limit this velocity and feed it in to the second PD controller. |
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This will output the desired acceleration. This is also limited. The acceleration is then integrated twice resulting in a position that is velocity and acceleration limited. |
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Which is fed in to the stepper motor model. |
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A nice feature of this setup is that has no feedback outside of the controller. |
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Therefore, we do not need any sensors in the system. |
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Maybe some initial setpoint. |
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