Multiple access communication is required to control multiple plants via wireless communication channels. This study discusses time division multiple access (TDMA) schemes to improve control quality for feedback control of multiple plants. To improve the control quality, time slot allocation of the TDMA should be based on information of the control layer, i.e., control objective and plant's state. In wireless control of multiple plants, there are different target values for the plants and different packet losses on communication channels. This leads to different tracking performances among the controlled plants. Therefore, a flexible time slot allocation scheme that considers the tracking performances is required. In this paper, we propose time slot allocation schemes to minimize predicted tracking error on the controlled plants. One minimizes the predicted tracking error in all time slots, and the other sequentially minimizes that in each time slot. Numerical results show that the proposed schemes can improve an overall control quality under packet loss.