Hi Changxin!
Sorry for my late response, somehow I didn't see your message.
Hm I wouldn't recommend using ONA directly to control the motors, since stability should be guaranteed to avoid damage to the hardware. (same with collision avoidance when distance becomes dangerously small)
Ideally ONA would control the drone on a higher-level: to let it move in various directions via operation invocations, whereby desired speed can be an operation argument.
Best regards,
Patrick