Vehicle control by pitch modulation
View Patent ↗A method for fore-aft stabilization of a vehicle for motion in a specified direction over an underlying surface. The vehicle has at least one forward wheel and at least one aft wheel, and the forward wheel is characterized by a force normal to the instantaneous direction of motion of the vehicle. A motor actuator drives each aft wheel, and a controller governs the motor actuator or motor actuators in such a manner as to dynamically stabilize the vehicle, according to a uniform control law, when the forward wheel is in contact with the underlying surface or not. A torque is applied to the aft wheel on the basis of vehicle pitch or the force on the forward wheel normal to the direction of motion. Additionally, a periodic rotational modulation may be applied to the aft wheel, and a stabilizing torque provided based on a detected response, either of vehicle pitch or of normal force on the front wheel. Left and right motor actuators may independently control left and right aft wheels to continue turns as governed by user steering, whether or not forward wheels are in contact with the ground.
1. An apparatus for pitch stabilization of the motion of a vehicle having at least one forward wheel and at least one aft wheel, the apparatus comprising:
a sensor for sensing a force on the forward wheel normal to an instantaneous direction of motion of the vehicle;
a motor actuator for driving the aft wheel; and
a controller for applying a torque to the aft wheel on the basis of a control law based at least on the normal force on the forward wheel;
wherein the controller causes the motor actuator to apply a periodic torque to the at least one aft wheel to induce a small pitch modulation.
2. An apparatus according to claim 1 , further comprising a second sensor for sensing a force on the forward wheel normal to the instantaneous direction of motion of the vehicle.
3. An apparatus according to claim 1 , further comprising:
a pitch detector to detect a pitch variation of the vehicle in response to the periodic torque;
wherein the controller causes the motor actuator to apply a stabilizing torque to the at least one aft wheel on the basis, at least, of any detected pitch variation in response to the applied periodic torque.
4. A stabilized vehicle comprising:
at least one forward wheel;
at least one aft wheel;
at least one sensor for sensing a force on the forward wheel normal to an instantaneous direction of motion of the vehicle;
at least one sensor for sensing an instantaneous pitch of the vehicle;
a motor actuator for driving the aft wheel; and a controller for applying a torque to the aft wheel on the basis of a control law based at least on the normal force on the forward wheel;
wherein the vehicle is a motorcycle.
5. A stabilized vehicle comprising:
at least one forward wheel;
at least one aft wheel;
at least one sensor for sensing a force on the forward wheel normal to an instantaneous direction of motion of the vehicle;
at least one sensor for sensing an instantaneous pitch of the vehicle;
a motor actuator for driving the aft wheel; and a controller for applying a torque to the aft wheel on the basis of a control law based at least on the normal force on the forward wheel;
wherein the vehicle is a wheelchair.
6. A stabilized vehicle according to claim 5 , wherein the controller controls operation of the vehicle in the same manner regardless of whether the forward wheel is in contact with a surface being traversed.
7. A stabilized vehicle comprising:
at least one forward wheel;
at least one aft wheel;
at least one sensor for sensing an instantaneous pitch of the vehicle;
a motor actuator for driving the aft wheel; and a controller for applying a torque to the aft wheel by commanding the motor actuator to drive the aft wheel on the basis of a control law based at least on a function of the instantaneous pitch of the vehicle;
wherein the vehicle is a motorcycle.
8. A stabilized vehicle comprising:
at least one forward wheel;
at least one aft wheel;
at least one sensor for sensing an instantaneous pitch of the vehicle;
a motor actuator for driving the aft wheel; and a controller for applying a torque to the aft wheel by commanding the motor actuator to drive the aft wheel on the basis of a control law based at least on a function of the instantaneous pitch of the vehicle;
wherein the vehicle is a wheelchair.