forked from Archive/PX4-Autopilot
131 lines
3.5 KiB
C
131 lines
3.5 KiB
C
/**
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* @file Generic control value mixing library.
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*
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* This library implements a generic mixer function that can be used
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* by any driver or subsytem that wants to combine several control signals
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* into a single output.
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*
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* Terminology
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* ===========
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*
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* control
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* A mixer input value, typically provided by some controlling
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* component of the system.
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*
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* actuator
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* The mixer output value.
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*
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* Mixing basics
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* =============
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*
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* An actuator derives its value from the combination of one or more
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* control values. Each of the control values is scaled according to
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* the actuator's configuration and then combined to produce the
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* actuator value, which may then be further scaled to suit the specific
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* output type.
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*
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* Internally, all scaling is performed using floating point values.
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* Inputs and outputs are clamped to the range -1.0 to 1.0.
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*
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* control control control
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* | | |
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* v v v
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* scale scale scale
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* | | |
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* | v |
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* +-------> mix <------+
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* |
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* scale
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* |
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* v
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* out
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*
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* Scaling
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* -------
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*
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* Each scaler allows the input value to be scaled independently for
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* inputs greater/less than zero. An offset can be applied to the output,
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* as well as lower and upper boundary constraints.
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* Negative scaling factors cause the output to be inverted (negative input
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* produces positive output).
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*
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* Scaler pseudocode:
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*
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* if (input < 0)
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* output = (input * NEGATIVE_SCALE) + OFFSET
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* else
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* output = (input * POSITIVE_SCALE) + OFFSET
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*
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* if (output < LOWER_LIMIT)
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* output = LOWER_LIMIT
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* if (output > UPPER_LIMIT)
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* output = UPPER_LIMIT
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*
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*
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* Mixing
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* ------
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*
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* Mixing is performed by summing the scaled control values.
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*
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*
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* Controls
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* --------
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*
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* Each mixer is presented with an array of controls from which it
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* selects the set that will be mixed for each actuator.
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*
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* The precise assignment of controls may vary depending on the
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* application, but the following assignments should be used
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* when appropriate.
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*
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* control | standard meaning
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* --------+-----------------------
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* 0 | roll
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* 1 | pitch
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* 2 | yaw
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* 3 | primary thrust
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*/
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struct MixScaler
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{
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unsigned control; /**< control consumed by this scaler */
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float negative_scale; /**< scale for inputs < 0 */
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float positive_scale; /**< scale for inputs > 0 */
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float offset; /**< bias applied to output */
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float lower_limit; /**< minimum output value */
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float upper_limit; /**< maximum output value */
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};
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struct MixMixer
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{
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unsigned control_count; /**< number of control scalers */
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struct MixScaler output_scaler; /**< scaler applied to mixer output */
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struct MixScaler control_scaler[0]; /**< array of control scalers */
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};
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__BEGIN_DECLS
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/**
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* Perform a mixer calculation.
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*
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* Note that the controls array is assumed to be sufficiently large for any control
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* index in the mixer.
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*
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* @param mixer Mixer configuration.
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* @param controls Array of input control values.
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* @return The mixed output.
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*/
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__EXPORT float mixer_mix(struct MixMixer *mixer, float *controls);
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/**
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* Check a mixer configuration for sanity.
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*
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* @param mixer The mixer configuration to be checked.
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* @param control_count The number of controls in the system.
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* @return Zero if the mixer configuration is sane,
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* nonzero otherwise.
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*/
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__EXPORT int mixer_check(struct MixMixer *mixer, unsigned control_count);
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__END_DECLS
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