I am using an MPPI controller to drive a robot capable of traveling bidirectionally with equal efficiency. I want to have different values for acceleration and deceleration. To achieve this, I set the acceleration by setting ax_max to 0.5 and the deceleration by setting ax_min to -1.5. These values are respected when the robot is traveling forward. However, when the robot is traveling backward, the acceleration value becomes the deceleration value, and vice versa.