Sensors play an important role in the control loop. Often they are considered to be a part of the plant and the interaction between the plant and sensor is disregarded. In this paper we investigate stability properties of the control loop when this interface is considered explicitly from an input/output perspective. Making the assumption that the sensor is stable, we provide a Youla type characterisation of all the sensors that renders the loop stable for a fixed plant and controller. When none of the sensors can provide the necessary performance it is time for sensor blending or a sensor reconfiguration. The simplest form of sensor fusion, i.e., a linear combination of the sensors, does not preserve stability of the control loop, in general. In order to design efficient algorithms that operate on the set of controllers or a set of sensors that fulfil a given property, e.g., stability or a norm bound, it is important to have an operation that preserves that property, i.e., a suitable blending method. This paper places the sensor blending problem in a more general context: an operation on stable sensors is given under which feedback stability is preserved and under which sensors form a group, the sensor group. Under the action of this group operation changes in different sensitivities can be also expressed in explicit terms. These results can be applied in the analysis and synthesis of schemes with sensor reconfiguration.
- Sensor blending
- Sensor parametrisation
ASJC Scopus subject areas
- Control and Systems Engineering