5-48
5-11-1
Time-proportional control
PID control produces a smooth control output signal. The control output value is suitable for operating the analog output
module connected to the process. Since the output is continuously turned on (at a certain level), this is called continuous control
in the process control field.
If continuous control is smooth and accurate, the cost of the PID control components (such as actuators and heater amplifiers) is
expensive. Simplified control is called time-proportional control. This method controls the actuator either on or off (no
intermediate). Control components with on/off control are less expensive than continuous control configurations.
This section describes how to convert the control output of the PID control to time-proportional control. Consider a mechanism
to control the process by turning the load on and off. The figure below shows a hot balloon crossing several mountains. In this
case, the route is a set point. The balloon operator repeats ON/OFF of the burner. It is the control output. The large amount of air
in the balloon efficiently averages the effect of the burner and converts heat into a continuous effect. The temperature and
altitude of a slowly changing balloon are process variables.
Time-proportional control approximates continuous control using its duty cycle (the ratio of on-time to off-time). The following
figure shows how a duty cycle approximates this level when successive levels are averaged by a large number of processes.
If the burner on/off time of the hot balloon is recorded, the effect of the burner on the temperature and altitude of
the balloon should probably be very close to this.
Off
On
期待する効果
オン
/
オフ制御
周期
オン
オフ
Cycle
Expected effect
On/Off control
ON
OFF
Summary of Contents for Kostac SJ-Ether Series
Page 1: ...English version of the KOSTAC SJ Ether series user s manual SJ ETHER USER M...
Page 12: ......
Page 13: ...1...
Page 14: ......
Page 88: ......
Page 89: ......
Page 113: ...3 24 Note Refer to 6 3 3 Module Assembly for connections and locks between modules...
Page 153: ......
Page 156: ...flashing OFF Not sent H W RX Green flashing Receiving H W OFF Not received H W...
Page 161: ...4 8...
Page 221: ......
Page 310: ...Chapter 7 Maintenance...
Page 311: ......