Before revision:  In contrast to the traditional model, the drift condition consists of two equations and two market prices of risk , respectively, uncertainty. Furthermore, we examine the connection to short rate models and discuss some examples .
After revision:  In contrast to the traditional model, the drift condition consists of two equations and two market prices of risk and uncertainty, respectively. The drift condition is still consistent with the classical one if there is no volatility uncertainty. Similar to the traditional model, the risk-neutral dynamics of the forward rate are completely determined by the diffusion coefficient. Furthermore, we obtain some classical term structures under volatility uncertainty as examples of our model .