I'm trying to move the actuator to positions 1,2,3.,..., 4000 as successive small steps in goal position mode but it frequently stops responding along the way. There is a minimum time requirement between sending successive goal positions? I'm keeping a delay of 100 ms between each package but even this way it doesn't seem to be working properly.
My main objective is to make some kind of measure for each position of the motor and for that I need the motor moving as fast and reproducible as possible.
I'm just a beginner with these servos, and I'm not sure if I fully understand your question.
Do you mean that you want to move the motor to a given position and, when it stops to take a measurement from something that is connected to the servo before moving to the next position.
Two ways come to mind.
The first is to set the velocity register to a specific value, know how far to move from the current position to the new one and calculate how long that will take. You can then delay that long after issuing the 'goal position' register update before taking the measurement.
The other way is to issue the 'goal position' update instruction and then read either the 'moving' register (that will tell you when the rotor stops) or the 'present position' register to see how far way it is. When it gets to the required position, take your measurement.
DYNAMIXEL is running based on the PID control algorithm, and Goal Position and Present Position may not always exactly same.
If you are trying to move in a very small step, you'll need to read the Present Position to estimate the actual position.
You can decrease the differences by increasing Position P gain, but having too much P gain will make the output horn oscillate at the goal position.
Please take a look at below video that I describe the effect of P gain along with differences between Goal Position and Present Position.
I'm now using velocity mode but having another problem. Once I set the dynamixel to one speed i can not change the velocity and neather stop it moving.
If you want to check your packets using DYNAMIXEL Wizard2 please refer to below eManual
Beta test version is available and it'll help you to analyze whether your packet is good or not.