Analytical Modelling of Nozzle Flapper Servo Valve to predict Hysteresis
2022-26-1133
05/26/2022
- Event
- Content
- The flow from a servo valve is dependent on the position of its spool, which is affected by the energy dissipative mechanisms inherent to the servo valve. The position achieved by the spool is controlled by the input electric current signal, i, to the servo valve. However, because of the dissipative mechanics, the position of the spool can be different for the same value of input current signal i, when i is achieved by increasing from an initial value i0, versus, when it is reached when decreasing from the maximum value, i-max. This phenomenon, called hysteresis, results in different volumetric flow from the valve for the same current i, as it is approached from i0 or from imax. The hysteresis of the servo valve has its cascading effect on the actuator that it controls. The actuator will output an unintended position as a result of the servo valve’s hysteresis and the results can be detrimental to the application. It is therefore necessary to have different methods to predict, measure and control the hysteresis of the servo valves. The purpose of this paper is to present an analytical approach to predict the hysteresis of a nozzle flapper type servo valve. The method presented in the paper models a simple stick-slip friction and provides a general framework into which more complex friction models could be incorporated into. The result of the proposed analytical approach could be compared with the results obtained from practical test data and the parameters could be adjusted to refine the analytical model with which hysteresis of the nozzle flapper type servo valve can be predicted. It also provides a basic approach that can be extended to other types of servo valve.
- Citation
- Rajamoni, K., Talore, S., and Navadkar, A., "Analytical Modelling of Nozzle Flapper Servo Valve to predict Hysteresis," SAE Technical Paper 2022-26-1133, 2022, .