I would like to control 18V BLDC motor of battery powered drill. What I want to do remake the drill to nut runner (torque wrench), so I need to sense a motor current which is proportional to motor torque. My controller will include microcontroller. Here are some questions:
What I plan to do is to create relationship table between current readings and torque (Nm) of a load, and save these values in a microcontroller memory. So when the torque wrencher reaches knowing current value, controller will know that the bolt or nut is wrenched with a fixed known torque and motor stops.
Thank you for your answers.
- How battery voltage discharge can affect motor current measurement depending on the same load (for example I would like to wrench the same nut ant the same torque Nm)? Does it will affect my current reading and the current will increase?
- Could I sense the BLDC motor current directly on the battery high side or do I need to sense it on all three the motor phases?
- Is it enough to sense only current to create closed loop torque control, or do I need some additional parameter for torque control based on the different battery discharge levels?
What I plan to do is to create relationship table between current readings and torque (Nm) of a load, and save these values in a microcontroller memory. So when the torque wrencher reaches knowing current value, controller will know that the bolt or nut is wrenched with a fixed known torque and motor stops.
Thank you for your answers.