Rotational Spring (AB)
Libraries:
Simscape /
Foundation Library /
Rotational /
Elements
Description
The Rotational Spring (AB) block represents an ideal spring with a linear relationship between torque and angular deformation.
where:
t is the torque of port B acting on port F.
K is the spring stiffness.
δ is the spring deformation.
θRel is the relative angle between ports.
θRelUnloaded is the relative angle when the spring is in unloaded state.
θB and θF are the absolute angles of ports B and F, respectively.
B and F are angle-based rotational conserving ports. Positive spring torque drives port F in the positive direction. The spring torque is positive for negative deformation.
Variables
To set the priority and initial target values for the block variables prior to simulation, use the Initial Targets section in the block dialog box or Property Inspector. For more information, see Set Priority and Initial Target for Block Variables.
Nominal values provide a way to specify the expected magnitude of a variable in a model. Using system scaling based on nominal values increases the simulation robustness. Nominal values can come from different sources, one of which is the Nominal Values section in the block dialog box or Property Inspector. For more information, see Modify Nominal Values for a Block Variable.
The correct way to initialize the block depends on its placement in the block diagram:
In general, specify any two variables as high-priority targets, for example, Torque and Relative angle, or Unloaded relative angle and Deformation. The exception is Torque and Deformation, because these two variables are proportional to each other.
If the spring is in series with a known torque, specify only Relative angle or Unloaded relative angle as a high-priority target.
If the spring is in parallel with a known relative angle, specify only Torque, Deformation, or Unloaded relative angle as a high-priority target.
If the spring is in series with a known torque and in parallel with a known relative angle, do not specify any high-priority targets.
Examples
Interpreting Angle in the Angle-Based Rotational Domain
Set up and interpret angles in angle-based rotational models. It provides background information to explain the underlying concepts. The angle-based rotational domain tracks angle, θ, and rotational velocity, ω, at every node. Use angle-based rotational blocks to model rotational systems where knowing multiple component angles is important.
Interpreting Torque in the Angle-Based Rotational Domain
Describes how to interpret torques in a Simscape™ angle-based rotational network. It outlines the key concepts for understanding the signs of logged torques. It examines rotational spring systems driven by torque sources at different ends, as well as a rotational system of inertias, to illustrate the torque behavior.
Ports
Conserving
Parameters
Extended Capabilities
Version History
Introduced in R2026a
