X-Y Cartesian manipulator and servomotors
Also available in: Català · Castellano
The idea
A Cartesian manipulator moves in straight lines along perpendicular axes (X, Y, and a Z cylinder to go down). It’s easy to calculate: each axis is independent.
Homing
At power-up, the system doesn’t know where the carriage is. Each axis moves until a reference sensor triggers (S9 for Y, S10 for X): that point becomes zero. Without homing, every coordinate would be wrong.
From millimetres to pulses
Each warehouse slot has coordinates in mm. The PLC converts them into pulses and sends them to the servo drives. On this model, 1 mm = 138.12 pulses.
Example: going to X = 120 mm → 120 × 138.12 ≈ 16,574 pulses.
Servomotor = closed loop
The drive receives the pulses and turns the motor; the encoder reports the real position and the drive corrects the difference. It’s the same closed loop as the PID.
The warehouse
16 slots: 0–7 for metallic parts and 8–15 for non-metallic ones. The PLC remembers which are occupied and with which part colour, so it can fill the orders placed from the HMI.
Safety
Light curtains watch the work area: if someone enters, the servo PLC stops the movement.
Interactive demo
Related concepts
Rotary encoders
An encoder tells the motor where it is. With two phase-shifted channels (A and B) you know how far it has turned and in which direction.
Closed-loop control (PID)
A PID compares what you want with what you measure and corrects using three terms: P looks at the present, I at the past and D at the future.
PLC and GRAFCET
A PLC cyclically reads all its inputs, runs the program and updates the outputs. GRAFCET describes the process as a sequence of steps and transitions: each step waits for a condition before moving to the next.