Servomotor control systems and methods

1. A radio controlled (RC) vehicle comprising:

a servomotor comprising a servomotor shaft;

a servomotor controller configured to generate one or more control signals for controlling the servomotor, wherein at least one of the control signals is a power control signal based at least in part on: (i) a rotational speed of the servomotor based at least in part on a back electromotive force measured at the servomotor, and (ii) a rotational direction of the servomotor;

wherein at least one of the control signals is a directional control signal based at least in part on an input received via a radio-controlled (RC) vehicle controller associated with the RC vehicle; and

wherein the power control signal is based at least in part on: (i) a proportional factor multiplied by a positional error, wherein the positional error is the difference between a desired rotational position of the servomotor shaft and a present rotational position of the servomotor shaft, (ii) a velocity factor multiplied by the product of a rotational speed of the servomotor and a rotational direction of the servomotor, and (iii) an integral factor multiplied by an integral of the servomotor positional error over time.

2. The RC vehicle of claim 1 , wherein the power control signal is determined according to the equation: power(t)=P(t)−V(t)+I(t);

wherein P(t)=K P (error(t)), wherein K P is a proportional gain factor, wherein error(t)=θ*(t)−θ(t), wherein θ*(t) is the desired rotational position of the servomotor shaft, and wherein θ(t) is the measured rotational position of the servomotor shaft;

wherein V(t)=K V ×direction(t)×speed(t), wherein K V is a velocity gain factor, wherein direction(t) is the direction of the servomotor, and wherein speed(t) is the speed of the servomotor; and

wherein I(t)=K I ×∫(error(t))dt, wherein K I is an integral gain factor, and wherein ∫(error(t))dt corresponds an integral of the positional error.

3. A radio controlled (RC) vehicle comprising:

a servomotor comprising a servomotor shaft;

a servomotor controller configured to generate one or more control signals for controlling the servomotor, wherein at least one of the control signals is a power control signal based at least in part on: (i) a rotation speed of the servomotor based at least in part on a back electromotive force measured at the servomotor, and (ii) a rotational direction of the servomotor; and

wherein the one or more control signals comprise one or more directional control signals, and wherein the RC vehicle further comprises:

an H-bridge circuit comprising four H-bridge terminals configurable to at least four states in response to the one or more directional control signals generated the servomotor controller; and

a voltage divider configured to measure a voltage corresponding to a back electromotive force (EMF) generated by the rotation of the servomotor;

wherein the first state enables current to flow across the servomotor from a first H-bridge terminal to a third H-bridge terminal to rotate the servomotor in a first direction;

wherein the second state enables current to flow across the servomotor from a second H-bridge terminal to a fourth H-bridge terminal to rotate the servomotor in a second direction;

wherein the third state creates a short across the first and second H-bridge terminals to cause the servomotor to brake; and

wherein the fourth state creates a short across the third and fourth H-bridge terminals to cause the servomotor to brake.

4. The RC vehicle of claim 3 , wherein the servomotor controller is configured to correlate the measured voltage corresponding to the back EMF with the rotational speed of the servomotor.

5. A system comprising:

a servomotor comprising a servomotor shaft; and

control circuitry configured to generate one or more control signals for controlling the servomotor and a rotational position of the servomotor shaft, wherein the one or more control signals are based at least in part on: (i) servomotor braking caused by shorting two terminals of an H-bridge circuit configured to control a rotational speed and a rotational direction of the servomotor; (ii) a servomotor rotational speed based at least in part on a back electromotive force measured at the servomotor, and (iii) a servomotor rotational direction;

wherein at least one control signal includes a power control signal determined according to the equation: power(t)=P(t)−V(t)+I(t);

wherein P(t)=K P (error(t)), wherein K P is a proportional gain factor, wherein error(t)=θ*(t)−θ(t), wherein θ*(t) is the desired rotational position of the servomotor shaft, and wherein θ(t) is the measured rotational position of the servomotor shaft;

wherein V(t)=K V ×direction(t)×speed(t), wherein K V is a velocity gain factor, wherein direction(t) is the direction of the servomotor, and wherein speed(t) is the speed of the servomotor; and

wherein I(t)=K I ×∫(error(t))dt, wherein K I is an integral gain factor, and wherein ∫(error(t))dt corresponds an integral of error(t).

6. A method of controlling a servomotor comprising a servomotor shaft, the method comprising:

determining a present rotational direction of the servomotor;

determining a present rotational speed of the servomotor based at least in part on a back electromotive force measured at the servomotor;

determining a present rotational velocity of the servomotor based at least in part on the determined rotational speed and determined rotational direction;

generating at least one power control signal for controlling an amount of current applied to the servomotor based at least in part on the determined rotational velocity; and

applying at least one servomotor control signal to the servomotor based at least in part on the at least one power control signal;

wherein the rotational direction of the servomotor is based at least in part on an input received from a radio-controlled (RC) vehicle controller associated with an RC vehicle;

calculating a positional error based on the difference between an actual rotational position of the servomotor shaft and a desired rotational position of the servomotor shaft;

calculating an integral of the servomotor positional error over time; and

wherein the at least one power control signal is based at least in part on the rotational velocity, the calculated positional error, and the calculated integral of the positional error.

7. The method of claim 6 , wherein the value of the at least one power control signal determined according to the equation: power(t)=P(t)−V(t)+I(t);

wherein P(t)=K P (error(t)), wherein K P is a proportional gain factor, wherein error(t)=θ*(t)−θ(t), wherein θ*(t) is the desired rotational position of the servomotor shaft, and wherein θ(t) is the measured rotational position of the servomotor shaft;

wherein V(t)=K V ×direction(t)×speed(t), wherein K V is a velocity gain factor, wherein direction(t) is the direction of the servomotor; and wherein speed(t) is the speed of the servomotor; and

wherein I(t)=K I ×(error(t))dt, wherein K I is an integral gain factor, and wherein ∫(error(t))dt corresponds an integral of the positional error.

8. The method of claim 6 , wherein determining a present rotational speed of the servomotor based at least in part on a back electromotive force measured at the servomotor comprises:

measuring a voltage at a node joining a voltage divider positioned across two terminals of the servomotor and an RC filter; and

correlating the measured voltage with a servomotor rotational speed.