System Identification of a Thermal Process

System identification of a linear time-invariant (LTI) system can be completed with time-domain or frequencydomain methods. • Time-domain system identification usually involves the analysis of a plant’s response to a step function on its input. Because a step function only takes two values, it can be generated by a digital output. • Frequency-domain system identification finds the gain and phase shift that the system realizes for several sinusoidal input signals of different frequency. Because a sinusoidal input swings through a continuous range of input values, it can only be generated by an analog output. Each LM35 temperature sensor is heated by an incandescent lamp that requires 100mA at 6V (i.e., like a 60Ω resistor). This current is provided by a DS2003 Darlington driver chip. This DS2003 is designed for on–off control of high current devices based on a digital input (including both TTL and CMOS logic). However, as long as we only use one DS2003 channel at at time, it can be used as a linear analog amplifier for frequency-domain system identification.