Throttle control for small engines and other applications

A method of controlling the throttle setting of an engine, the engine including a throttle, and an actuator, the engine operating at a speed in accordance with the setting of the throttle, the actuator, responsive to control signals applied thereto and having a plurality of discrete activation states associated therewith, controlling the setting of the throttle, the method comprising the steps of:

• selectively generating control signals to said actuator corresponding to a first activation state;
• selectively generating control signals to said actuator corresponding to a second activation state;
• and
• dithering between the respective activation states at a predetermined frequency.

For apparatus including an engine having a throttle and an actuator, the engine

• operating at a speed in accordance with the setting of the throttle, wherein the actuator is responsive to control signals applied thereto and has a plurality of discrete activation states associated therewith, a method of increasing control resolution whereby at least a first intermediate throttle setting is provided between throttle settings corresponding to first and second discrete activation states, the method comprising the steps of:
• (a) generating, for a first predetermined time period, control signals corresponding to the first activation state;
• (b) then generating, for a second predetermined time period, control signals corresponding to the second activation state;
• and
• (c) for so long as the first intermediate activation state is maintained, repeating steps (a) and (b), dithering between the first and second activation states.

A method of controlling the throttle setting of an engine, the engine including a throttle, and an actuator, the engine operating at a speed in accordance with the setting of the throttle, the actuator, responsive to control signals applied thereto and having a plurality of discrete activation states associated therewith, controlling the setting of the throttle, the method comprising the steps of:

• (a) generating, for a first predetermined time period, control signals corresponding to a first activation state;
• (b) then generating, for a second predetermined time period, control signals corresponding to a second activation state;
• and
• (c) repeating steps (a) and (b), thereby dithering between the first and second activation states.

For apparatus including an the engine having a throttle and an actuator, the engine operating at a speed in accordance with the setting of the throttle, wherein the actuator is responsive to control signals applied thereto and has a plurality of discrete activation states associated therewith, a method of increasing control resolution whereby at least a first intermediate throttle setting is provided between throttle settings corresponding to first and second discrete activation states, the method comprising the steps of:

• (a) generating, for a first predetermined time period, control signals corresponding to the first activation state;
• (b) then generating, for a second predetermined time period, control signals corresponding to the second activation state;
• and
• (c) for so long as the first intermediate activation state is maintained, repeating steps (a) and (b), dithering between the first and second activation states.

Apparatus for controlling the throttle setting of an engine, comprising:

• an actuator, responsive to control signals applied thereto, for controlling the setting of the throttle;
• and
• a control circuit, for generating the control signals to the actuator;
• wherein the actuator comprises:
• a throttle lever arm adapted to cooperate with the throttle such that the throttle setting varies in accordance with the position of the throttle lever arm;
• an elongated magnet, magnetized through the length thereof, a non-magnetic coupling between the magnet and throttle arm, such that movement of the magnet effects a corresponding movement of the throttle arm;
• an electrical coil, receptive of a control signal applied thereto, and disposed such that current flow therethrough effects magnetic interaction with the magnet, causing the magnet to assume a position in accordance with the power through the coil, to control the position of the throttle arm.

Apparatus for controlling the throttle setting of an engine, the engine having a mechanical response time to throttle setting changes, comprising:

• an actuator, responsive to control signals applied thereto, for controlling the setting of the throttle;
• and
• a control circuit, for generating the control signals to the actuator;
• wherein the actuator comprises:
• a stepping motor having a rotor with magnetic components and plurality of stator coils, the stator coils having an inductive rise time associated therewith;
• a drive circuit, responsive to control signals applied thereto, for selectively effecting current flow through designated coils, the stepping motor having a plurality of activation states associated therewith, each such activation state corresponding to current flow through a corresponding predetermined activated coil set, each set comprising at least a portion of at least one stepping motor coil, current flow through an activated coil set generating magnetic fields to interact with the magnetic components of the rotor, and tending to cause the rotor to assume a predetermined alignment with said fields;
• a mechanical coupling between the stepping motor shaft and the engine throttle, such that rotary movement of the stepping motor shaft effects control of the throttle setting;
• and
• wherein the control circuit selectively generates signals to the drive circuit to dither between successive coil actuation states, the engine has a mechanical response time associated therewith;
• the actuator stator coils have an inductive rise time associated therewith;
• and
• dithering between respective coil actuation states is effected at a rate faster than the mechanical response time of the engine but less than the inductive rise time of the actuator stator coils, the actuator stator coils have an inductive rise time associated therewith;
• the actuator rotor has a mechanical response time associated therewith when coupled to the throttle;
• and
• dithering between respective coil actuation states is effected at a rate faster than the mechanical response time of the actuator but less than the inductive rise time of the stator coils comprises a microcomputer selectively generates control signals to said drive circuit to effect current paths through at least portions of the respective stepping motor coils in predetermined sequences to cause the rotary shaft to move in predetermined increments.