Yaskawa MP920 User's Manual Design - Manual (Page 133)

4.2 Control Modes
4-19
4
„ User Program Example 2: Electronic Cam
Example of RUN Operation
Cams are one of the conventional methods for changing a rotational movement to a linear
movement, and they are used to obtain the desired operation curve (displacement drawing)
during a cycle.
• A mechanical cam forms a cam with a shape corresponding to this displacement drawing.
Placing a follower on the circumference and rotating the cam enables the desired linear
operation to be obtained.
• An electronic cam holds the actual displacement drawing data in the controller as a posi-
tion pattern, and performs regular position control for the so-called continuous path (CP)
by changing the phase.
An electronic cam control loop can be configured using phase control. With normal phase
control, the position reference is generated by integrating the reference speed reference into
the SVA Module (see Fig. 4.8).
An electronic cam control loop cuts the integral circuit of the reference speed reference, and
provides the position reference from the phase compensation settings (see Fig. 4.9).
The following illustration shows a block diagram of a phase control loop.
S
Xref
+
+
+ -
+
-
M
PG
M
MP920
Mechanical cam
Follower displacement
Phase θ
Follower When the mechanical cam
rotates, the follower moves
linearly, as shown in the
displacement drawing.
Phase
refer-
ence
θ
Displacement pattern generation
Position control
Encoder
Ball screw
Follower
Follower displacement
Servo
motor
Phase
Speed
control
Mechanical cam
Electronic cam
θ