backlash

This no_std Rust crate implements a processor that introduces backlash into continuous values similar to what happens in mechanical systems.

In most cases, backlash is an unwanted effect, but sometimes it can be utilized for signal conditioning by reducing back-and-forth jumping of unstable values. A typical use case is when reading a potentiometer (via ADC) in an embedded system for the purpose of generating events on movement.

The advantage over using a simple deadband method is to achieve an output signal without discontinuity when the direction of movement changes. In case of a potentiometer, it allows to tweak a setting without noticable jumps when changing the direction.

Important:

• Backlash is not similar to hysteresis, which does not introduce a deadband but a shift.
• Don't use backlash when precision is required. It creates non-linearity and reduces the value range of the input by the amount of the configured deadband.
• Introducing backlash is not a replacement for conventional smoothing. Any filtering may be still required and should be performed prior to this processor.

Usage Example

use backlash::Backlash;

// The width of the deadband.
const DEADBAND_WIDTH: i32 = 10;

// Create an instance of the processor using `i32` values.
// Floating point types like `f32` are also supported.
let mut backlash = Backlash::<i32>::new(DEADBAND_WIDTH);

// These are some simulated input values from a pot moving upwards from 90 to 100
// with some instability when settled.
let input_values = [90, 95, 98, 99, 100, 99, 98, 99, 100, 99];

for input_value in input_values {
    // Process the input and get the output value.
    let output_value = backlash.update(input_value);

    // The output values will raise from 85 to 95 and then stay there.
    println!("{}", output_value);
}

// Now the pot will be turned down to 50, also with some instability at the end.
let input_values = [100, 80, 60, 55, 50, 52, 51, 50, 51, 52];

for input_value in input_values {
    // Process the input and get the output value.
    let output_value = backlash.update(input_value);

    // The output values will fall from 95 to 55 and then stay there.
    println!("{}", output_value);
}

Tests

Run cargo test for the unit tests.

License

Published under the MIT license. Any contribution to this project must be provided under the same license conditions.

Author: Oliver Rockstedt info@sourcebox.de