<P> Hardware - in - the - loop (HIL) simulation, or HWIL, is a technique that is used in the development and test of complex real - time embedded systems . HIL simulation provides an effective platform by adding the complexity of the plant under control to the test platform . The complexity of the plant under control is included in test and development by adding a mathematical representation of all related dynamic systems . These mathematical representations are referred to as the "plant simulation". The embedded system to be tested interacts with this plant simulation . </P> <P> A HIL simulation must include electrical emulation of sensors and actuators . These electrical emulations act as the interface between the plant simulation and the embedded system under test . The value of each electrically emulated sensor is controlled by the plant simulation and is read by the embedded system under test (feedback). Likewise, the embedded system under test implements its control algorithms by outputting actuator control signals . Changes in the control signals result in changes to variable values in the plant simulation . </P> <P> For example, a HIL simulation platform for the development of automotive anti-lock braking systems may have mathematical representations for each of the following subsystems in the plant simulation: </P> <Ul> <Li> Vehicle dynamics, such as suspension, wheels, tires, roll, pitch and yaw; </Li> <Li> Dynamics of the brake system's hydraulic components; </Li> <Li> Road characteristics . </Li> </Ul>

Hardware in the loop vs processor in the loop