Customer is using STM32L4 and L6235Q

[EHD]

The customer was looking for a lock function from its BLDC motor driver. They were advised to use the “dynamic braking�? function of their motor driver, it seems - from what I understand. The Dynamic braking function does not offer a true locking functionality, unfortunately. Dynamic braking will allow the motor to drift from a stopped position, if the load can overcome the mechanical frictions and backdrive the motor and its transmission. Think of it as adding a lot of viscosity into a mechanism; that’s what the Dynamic Braking functionality of a BLDC motor driver chip provides. In the customer’s situation, closing the loop on position (simple Proportional closed-loop is probably sufficient in this case) would keep motor in its stopped position, even if the load tries to backdrive the motor. 

Application: Tourniquet. After reaching proper pressure, the tourniquet must stay in position not to allow the release of pressure. Dynamic Braking will allow a slow release of the pressure, which is unwanted, in this case. A closed loop system in the MCU would prevent pressure release when in stopped position.

[Cristiana SCARAMEL]

Hello @EHD​,

the L6235 Brake function can be used to quickly stop the motor while it is running (making a short-circuit across the motor windings).

If you want to keep a position it is necessary to apply a torque.

If I understood well the application if you limit the torque is like holding the tourniquet in tension with a maximum constant force.