ROTATION-ACCELEROMETER

Connection type ROTATION-ACCELEROMETER provides a convenient way to measure the relative angular position, velocity, and acceleration of a body in a local coordinate system. These kinematic quantities are measured relative to the motion of node a and are reported in the coordinate system of node b. Each node of the connector can translate and rotate independently, although fixing the first of the two nodes to ground is more common. With the first node fixed, connection type ROTATION-ACCELEROMETER provides a convenient way to measure the local components of the angular velocity and angular acceleration in a coordinate system fixed to a moving body (for example, an accelerometer).

Connection type ROTATION-ACCELEROMETER is available only in Abaqus/Explicit. It is the rotation counterpart to connection type ACCELEROMETER, which measures relative translational position, velocity, and acceleration.

ROTATION-ACCELEROMETER connectors cannot be used in two-dimensional and axisymmetric analysis in Abaqus/Explicit.

Related Topics
Connector elements
Connector element library
In Other Guides
*CONNECTOR BEHAVIOR
*CONNECTOR SECTION

ProductsAbaqus/ExplicitAbaqus/CAE

Description

Figure 1. Connection type ROTATION-ACCELEROMETER.

The ROTATION-ACCELEROMETER connection does not impose kinematic constraints. It defines three local directions at node a and three local directions at node b. The ROTATION-ACCELEROMETER connection's formulation is similar to that for the ROTATION connection. The ROTATION-ACCELEROMETER connection measures the finite rotation that takes the local directions at node a into the local directions at node b and parameterizes that finite rotation by the rotation vector. Let ϕ be the rotation vector that positions local directions {e1b,e2b,e3b} relative to {e1a,e2a,e3a}; that is,

eib=exp[ϕ^]eia

for all i=1,2,3, where ϕ^ is the skew-symmetric matrix with axial vector ϕ. See Rotation variables for a discussion of finite rotations. The connection measures the change in the rotation vector components in the local directions rotating with the body at node b. The rotation vector components are calculated as

ϕi=eibϕ.

There are no available components of relative motion for the ROTATION-ACCELEROMETER connection. The connector rotation is

uri=ϕi-(ϕ0)i+2nπϕiϕ,

where ϕ0 is the initial rotation vector and n0 is an integer accounting for rotations with magnitude greater than 2π.

The ROTATION-ACCELEROMETER connection differs from the ROTATION connection in the way angular velocity and acceleration are calculated. The ROTATION-ACCELEROMETER connection measures velocity and acceleration from the nodes as

vri=(ωb-ωa)eib    and    ari=(αb-αa)eib,

where ωa, ωb, αa, and αb are the nodal angular velocities and accelerations at nodes a and b, respectively.

In two-dimensional and axisymmetric analyses ur1=ur2=0.

Summary

ROTATION-ACCELEROMETER
Basic, assembled, or complex: Basic
Kinematic constraints: None
Constraint force output: None
Available components: None
Kinetic force output: None
Orientation at a: Optional
Orientation at b: Optional
Connector stops: None
Constitutive reference lengths: None
Predefined friction parameters: None
Contact force for predefined friction: None