# simscape.multibody.TorsionalSpringDamper class

Package: simscape.multibody
Superclasses: `simscape.multibody.JointForceLaw`

Construct torsional spring-damper force law

## Description

Use an object of the `simscape.multibody.TorsionalSpringDamper` class to construct a torsional spring-damper force law. You can use the force law to apply a pure torque to a `simscape.multibody.RevolutePrimitive` object. The torque is based on the current position and velocity of the primitive

$T=-{k}_{s}·\left(q-{q}_{0}\right)-{k}_{d}\stackrel{˙}{q}$,

where:

SymbolDescription
$T$Applied torque
${q}_{0}$Equilibrium position of the spring
${k}_{s}$Spring stiffness
${k}_{d}$Damping coefficient
$q$Revolute primitive position
$\stackrel{˙}{q}$Revolute primitive velocity

### Class Attributes

 `Sealed` `true` `ConstructOnLoad` `true` `RestrictsSubclassing` `true`

For information on class attributes, see Class Attributes.

## Creation

### Description

`tsd = simscape.multibody.TorsionalSpringDamper` constructs a torsional spring-damper force law and sets the parameters to `simscape.Value` objects with a value of zero.

## Properties

expand all

Equilibrium position of the torsional spring, specified as a `simscape.Value` object that represents a scalar with a unit of angle. The scalar can be positive, negative, or zero. The torque is zero when the primitive position is at the equilibrium position.

Example: `simscape.Value(10,"deg")`

#### Attributes:

 `GetAccess` `public` `SetAccess` `public` `NonCopyable` `true`

Stiffness of the torsional spring, specified as a `simscape.Value` object that represents a scalar with a unit of torque/angle. The scalar is a measure of how hard the spring pushes the primitive position toward the equilibrium position and must be nonnegative.

Example: `simscape.Value(5,"N*m/deg")`

#### Attributes:

 `GetAccess` `public` `SetAccess` `public` `NonCopyable` `true`

Damping coefficient of the damper, specified as a `simscape.Value` object that represents a scalar with a unit of torque/angular velocity. The scalar is a measure of how hard the damper resists the motion of a primitive and must be nonnegative.

Example: `simscape.Value(10,"N*m/(deg/s))`

#### Attributes:

 `GetAccess` `public` `SetAccess` `public` `NonCopyable` `true`

## Version History

Introduced in R2022a