forked from Archive/PX4-Autopilot
237 lines
7.8 KiB
C
237 lines
7.8 KiB
C
/****************************************************************************
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*
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* Copyright (C) 2012 PX4 Development Team. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name PX4 nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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#ifndef _SYSTEMLIB_MIXER_H
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#define _SYSTEMLIB_MIXER_H
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/**
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* @file mixer.h
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*
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* 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 value
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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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* control group
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* A collection of controls provided by a single controlling component.
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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 scaler_s {
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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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uint8_t control_group; /**< control group this scaler reads from */
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uint8_t control_index; /**< control index within the group */
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};
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struct mixer_s {
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unsigned control_count; /**< number of control scalers */
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struct scaler_s output_scaler; /**< scaler applied to mixer output */
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struct scaler_s control_scaler[0]; /**< array of control scalers */
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};
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/**
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* Handy macro for determining the allocation size of a mixer.
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*/
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#define MIXER_SIZE(_num_scalers) (sizeof(struct mixer_s) + ((_num_scalers) * sizeof(struct scaler_s)))
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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, and the arrays it indexes, are assumed
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* to be sufficiently large for any control index in the mixer.
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*
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* @param mixer Mixer configuration.
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* @param controls Array of pointers to control group values.
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* @return The mixed output.
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*/
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__EXPORT float mixer_mix(struct mixer_s *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 group_count The highest-numbered control group that
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* should be considered legal.
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* @param control_count The highest control index that should be
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* considered legal.
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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 mixer_s *mixer, unsigned group_count, unsigned control_count);
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/**
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* Evaluate the control inputs to a mixer and update the bitmask of
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* required control groups.
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*
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* This function allows an actuator driver to selectively fetch just
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* the control groups required to support a particular mixer or set of
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* mixers.
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*
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* @param mixer The mixer being evaluated.
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* @param groups Pointer to a bitmask to be updated with set bits
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* corresponding to the control groups used by the
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* mixer.
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*/
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__EXPORT void mixer_requires(struct mixer_s *mixer, uint32_t *groups);
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/**
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* Read a mixer definition from a file.
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*
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* A mixer definition is a text representation of the configuration of a
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* mixer. The definition consists of a single-line header indicating the
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* number of scalers and then one line defining each scaler. The first
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* scaler in the file is always the output scaler, followed by the input
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* scalers.
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*
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* M: <scaler count>
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* S: <control group> <control index> <negative_scale*> <positive_scale*> <offset*> <lower_limit*> <upper_limit*>
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* S: ...
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*
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* The <control ...> values for the output scaler are ignored by the mixer.
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*
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* Values marked * are integers representing floating point values; values are
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* scaled by 10000 on load/save.
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*
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* Multiple mixer definitions may be stored in a single file; it is assumed that
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* the reader will know how many to expect and read accordingly.
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*
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* A mixer entry with a scaler count of zero indicates a disabled mixer. This
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* will return NULL for the mixer when processed by this function, and will be
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* generated by passing NULL as the mixer to mixer_save.
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*
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* @param fd The file to read the definitions from.
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* @param mixer Mixer is returned here.
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* @return 1 if a mixer was read, zero on EOF or negative on error.
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*/
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__EXPORT int mixer_load(int fd, struct mixer_s **mixer);
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/**
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* Save a mixer definition to a file.
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*
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* @param fd The file to write the definitions to.
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* @param mixer The mixer definition to save.
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* @return Zero on success, negative on error.
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*/
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__EXPORT int mixer_save(int fd, struct mixer_s *mixers);
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__END_DECLS
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#endif /* _SYSTEMLIB_MIXER_H */
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