Abstract: Capture zone simulation requires several timeconsuming trajectory integrations. However, the change of situation is very fast and demands the information of capture zone in real time. In order to compute the information of capture zone in real time, this paper suggests a background interpolation strategy for capture zone online simulation. Firstly, the value of the state variables at the next sample time is predicted according to the state equations. And the capture zone at the predicted state is simulated. Secondly, when the next sample time arrives, the predicted values of capture zone in the current cycle and the previous two cycles, as well as the corresponding state values, are used to interpolate the true capture zone value in current cycle. In this manner, the timeconsuming processes of trajectory integration is removed into the background. Thus, the interpolation is the only operation that delays the capture zone information. The theoritical analysis proves that the error of interpolation converges to zero as the sample interval decreases. Simulation results show that the errors of the background interpolation method and the traditional capture zone simulation are almost the same, and the average time delays are 7.16×10^-6 and 0.290 second, respectively.

Key words: capture zone, trajectory simulation, interpolation method