Denso SMT7 - Chapter 2 Engineering Design of Servo Mechanism; Designing the Servo Mechanism

Chapter 2 Engineering Design of Servo Mechanism
12
Chapter 2 Engineering Design of Servo Mechanism
2.1 Designing the Servo Mechanism
2.1.1 Example of the Mechanism
The mechanism is classified into a linear movement section and a revolving arm section as shown
in Fig. 2-1.
(a) Linear movement section (b) Revolving arm
Fig. 2-1 Example of the mechanism
2.1.2 Selection of the Drive System
An appropriate control cannot be performed if a rapid torque fluctuation occurs due to stick slip
or the like.
Typical appropriate and inappropriate examples of the drive system are as shown below:
 Ball screw Grinding Backlash small 
Rolling Backlash large (Control instable) 
 Gear Grinding Accuracy grade 1 or higher Backlash small 
Cutting Accuracy grade 3 or higher Backlash medium 
Accuracy grade 4 or lower Backlash large

 Screw shaft Friction large

 Harmonic drive Friction large 
(Care for selection)
 Slide section bearing linear motion bearing 
LM guide 
Slide bearing

 Seal, packing Friction: 20% or less of the rated torque in conversion
into the motor shaft's 
Friction: More than 20% of the rated torque in conversion
into the motor shaft's

 denotes "Appropriate"
 denotes "Conditionally appropriate"
 denotes "Inappropriate"
Ball screw, etc.
Load
Moto
r
Coupling
Load
Gea
r
Motor
Arm
Friction large