Motion control is control of actuators, like motors for example. Open loop means driving the motor with no feedback source. Closed loop, alternatively, means using a feedback source like an encoder or other sensors to measure the position or velocity of the motor, and then using software that monitors that sensor and adjusts the control parameters to ensure that the desired position, velocity, and/or acceleration is achieved. This is referred to as “closing the loop” because you have the controller going to the motor as one half of the loop, and the encoder going back to the controller (and the control system code) as the other half of the loop.
Precise motion control often uses control loops (the loop of code that checks the sensor and adjusts the output) that run at 20 kilohertz, 40 kilohertz, or higher. Since the control loop is a bunch of lines of code, this means you want to execute a bunch of lines of code repeatedly at this high rate of speed. For example on an 8Mhz micro controller clock running a 40 kilohertz loop, there’s only enough time to run 200 instructions per loop! (8Mhz/40kHz=200) 200 instructions isn’t a lot, so it would be tough to run a complex motion control loop in that space. And if you want to run multiple control loops to control multiple motors - forget it.
The teensy 32 bit micro controllers are a lot faster - I see a 72mhz and 180mhz option. Either of those would be solid for motion control. However if you want to control multiple motors and possibly perform some other functions, such as computing motion commands from G code in the case of a 3D printer control board, you need all the speed you can get. In that case, these new boards offer plenty of clock speed to play with!
Precise motion control often uses control loops (the loop of code that checks the sensor and adjusts the output) that run at 20 kilohertz, 40 kilohertz, or higher. Since the control loop is a bunch of lines of code, this means you want to execute a bunch of lines of code repeatedly at this high rate of speed. For example on an 8Mhz micro controller clock running a 40 kilohertz loop, there’s only enough time to run 200 instructions per loop! (8Mhz/40kHz=200) 200 instructions isn’t a lot, so it would be tough to run a complex motion control loop in that space. And if you want to run multiple control loops to control multiple motors - forget it.
The teensy 32 bit micro controllers are a lot faster - I see a 72mhz and 180mhz option. Either of those would be solid for motion control. However if you want to control multiple motors and possibly perform some other functions, such as computing motion commands from G code in the case of a 3D printer control board, you need all the speed you can get. In that case, these new boards offer plenty of clock speed to play with!