We have now a working installation that is a big 'jar' of liquid cupper (100ton).
It is rotated by a hydraulic motor on each side of the jar. The hydraulic motors are directly coupled on the rotation axis of the jar (no gearbox).
On the hydraulic motor there is an encoder (absolute position, 16bit) also directly on the axis (360° of the jar = 360° of the encoder).
The hydraulic motors are fed by a proportional valve that on its turn is fed by a constant pressure pump. The construction can be considered 'stiff' towards both sides of the rotation axis.
Now when the jar needs to be kept in constant position we use e position loop with the encoder on the motor. When we rotate the jar, we do it in 'open loop' : the proportional valve is opened in direct relation with the position of a joystick without influence of the encoder. When the joystick is back a zero position, we go to position loop again to maintain the position of the jar.
The concept of position loop at when holding position and open loop when rotating was proposed by the hydraulic constructor.
Now we were asked to do the rotation also in closed loop.
But I have my doubts, because in the very beginning I have tested this and the movement was not fluent. I suppose because of the resolution of the encoder.
Details : speed of the jar when the proportional valve is 100% opened : +- 1°/sec, encoder : 16 bits directly on the axis of the jar. Cycle time of the position loop in the controller : 1 ms. The speed can be chosen manually with a joystick. Speeds should be possible between 5% and 90% of the maximum (1°/sec). Now the position loop (for holding static position) is a pure proportional controller.
What resolution of the encoder should we at least have for fluent movements?
It is rotated by a hydraulic motor on each side of the jar. The hydraulic motors are directly coupled on the rotation axis of the jar (no gearbox).
On the hydraulic motor there is an encoder (absolute position, 16bit) also directly on the axis (360° of the jar = 360° of the encoder).
The hydraulic motors are fed by a proportional valve that on its turn is fed by a constant pressure pump. The construction can be considered 'stiff' towards both sides of the rotation axis.
Now when the jar needs to be kept in constant position we use e position loop with the encoder on the motor. When we rotate the jar, we do it in 'open loop' : the proportional valve is opened in direct relation with the position of a joystick without influence of the encoder. When the joystick is back a zero position, we go to position loop again to maintain the position of the jar.
The concept of position loop at when holding position and open loop when rotating was proposed by the hydraulic constructor.
Now we were asked to do the rotation also in closed loop.
But I have my doubts, because in the very beginning I have tested this and the movement was not fluent. I suppose because of the resolution of the encoder.
Details : speed of the jar when the proportional valve is 100% opened : +- 1°/sec, encoder : 16 bits directly on the axis of the jar. Cycle time of the position loop in the controller : 1 ms. The speed can be chosen manually with a joystick. Speeds should be possible between 5% and 90% of the maximum (1°/sec). Now the position loop (for holding static position) is a pure proportional controller.
What resolution of the encoder should we at least have for fluent movements?