Page 532 - Mechatronics with Experiments

JWST499-Cetinkunt
JWST499-c07
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Below is a pseudo-code for the control algorithm,
Home_Motion_Sequence() ;
while(true)
{
1. Wait until cycle start command is received, or
trigger signal is ON or a pre-defined time
period expires,
2. Enable position servo mode and move forward
with desired motion profile,
3. Monitor pressure differential and switch mode
if it reaches above a certain value when
cylinder position is within the defined limits,
4. Operate in force servo mode until the pre-defined time
period expired,
5. Then swicth to position servo mode and command
reverse motion to home position.

}
void function PID_Position(x_d, v_d)
{
static float K_p = 1.0, K_d = 0.0, K_i=0.01 ;
static float u_i = 0.0 ;
static Scale = 1.0 ;

u_i = u_i + K_i * (x_d - Scale * ENC) ;
DAC = K_p * (x_d - Scale * ENC) + u_i ;
return ;
}
void function PID_Force(F_d)
{
static float K_pf = 1.0, K_df = 0.0, K_if=0.01 ;
static float u_if = 0.0 ;
static float A1= 0.025, A2=0.0125 ;

u_if = u_if + K_if * (F_d - (P1*A1-P2*A2)) ;
DAC = K_pf * (F_d - (P1*A1-P2*A2)) + u_if ;
return ;
}

7.7 HYDRAULIC MOTION AXIS NATURAL FREQUENCY AND
BANDWIDTH LIMIT

As a general “rule of thumb,” a control system should aim to limit the bandwidth of the
closed loop system (w ) to less than 1∕3 of the natural frequency (w ) of the open loop
n
bw
system,
1
w < w (7.294)
bw n
3
Otherwise, too large closed loop control gains will result in closed loop instability or a
very lightly damped oscillatory response, therefore, it is important to estimate the open
loop natural frequency of a given EH motion axis. The most significant factors affecting