Struct SolImp 

pub struct SolImp {
    pub dmin: f64,
    pub dmax: f64,
    pub width: f64,
    pub midpoint: f64,
    pub power: f64,
}

MuJoCo-style solimp: constraint impedance as a function of the violation.

Impedance d in (0, 1) blends between a fully soft constraint (d -> 0, no force at all) and a fully rigid one (d -> 1). Making it depend on penetration depth is the point: a contact that has just been made is soft, so making and breaking contact stays smooth (and differentiable), while a deeply penetrating contact stiffens up and pushes hard.

Fields

dmin: f64

Impedance at zero violation.

dmax: f64

Impedance at and beyond width of violation.

width: f64

Violation (in metres, for contacts) over which dmin -> dmax.

midpoint: f64

Where in [0, 1] the sigmoid’s inflection sits.

power: f64

Sigmoid power. 1 is linear; larger is flatter at both ends.

Implementations

impl SolImp

pub fn impedance(&self, r: f64) -> f64

Impedance at a constraint violation of r metres.

The interpolant is MuJoCo’s polynomial sigmoid: a x^p below the midpoint and 1 - b (1-x)^p above it, with a and b chosen so the halves meet at the midpoint. It is C^1 in r everywhere except the clamp at x = 1.

pub fn impedance_derivative(&self, r: f64) -> f64

d(impedance)/dr at a non-negative violation r.

Mirrors Self::impedance branch for branch, including its clamps: past width the impedance is pinned at dmax, so the derivative is zero, and a non-positive width makes it constant everywhere.

Defined for r >= 0 only. impedance takes r.abs(), so the function has a kink at the origin whenever power == 1; for power > 1 (the default) both one-sided derivatives are zero there and this returns the value that is correct from either side.

Trait Implementations

impl Clone for SolImp

fn clone(&self) -> SolImp

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for SolImp

impl Debug for SolImp

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for SolImp

fn default() -> Self

Returns the “default value” for a type.

impl PartialEq for SolImp

fn eq(&self, other: &SolImp) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for SolImp