Rotational Hard Stop
Double-sided rotary rigid stop.
Description
The Rotational Hard Stop block is a bilateral mechanical hard stop that restricts body rotation between the upper and lower limits of angular position. Both ports of the block are of the mechanical rotational type. The impact interaction between the shaft and the limiters is assumed to be elastic. The limiter is in the form of a spring which comes into contact with the shaft when the clearance is eliminated. The spring counteracts the movement of the shaft inside the limiter with a torque linearly proportional to the magnitude of this movement. To account for energy dissipation and inelastic effects, damping is introduced as a block parameter to allow for energy losses.
The basic stiff stopping model, Full stiffness and damping applied at bounds, damped rebound, is described by the following equations:
where
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- is the torque between shaft and housing.
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- is the initial angle between the shaft and the upper limit of the angular position.
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- Starting angle between the shaft and the lower limit of the angular position.
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- angular position of the shaft.
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- contact stiffness at the upper boundary.
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- contact stiffness at the lower boundary.
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- damping coefficient at the upper boundary.
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- damping coefficient at the lower boundary.
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- angular velocity of the shaft.
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- time.
In the `Full stiffness and damping applied at bounds, undamped rebound' model, the equations contain additional terms, and . These terms ensure that no damping is applied at bounds, undamped rebound.
The By default hard stop model, Stiffness and damping applied smoothly through transition region, damped rebound', adds two transition regions to the equations, one at each boundary. As the shaft moves through the transition region, the block smoothly increases the torque from zero to the full value. At the end of the transition region, full stiffness and damping are applied. At rebound, both stiffness and damping moments smoothly decrease back to zero. The comparison functions `ge and le are also used in these equations.
The block is orientated from R to C. This means that the block transfers torque from port R to port C when the gap in the positive direction is closed.
Ports
R - shaft
`rotational mechanics
A mechanical rotary port corresponding to a shaft that rotates between stops mounted on the housing.
C - housing
`rotational mechanics
Mechanical rotational port corresponding to the hull.
Parameters
Upper bound, rad - initial angle between shaft and upper boundary
0.1 rad (by default)
The angle between the shaft and the upper boundary. The direction is set in the local coordinate system, with the shaft at its starting point. A positive value of the parameter defines the initial angle between the shaft and the upper boundary. A negative value defines the shaft as penetrating the upper boundary.
Lower bound, rad - the initial angle between the shaft and the lower boundary
-0.1 rad (By default).
The angle between the shaft and the lower boundary. The direction is set in the local coordinate system, with the shaft at its starting point. A negative value of the parameter defines the initial angle between the shaft and the upper boundary. A positive value defines the shaft as penetrating the upper boundary.
Contact stiffness at upper boundary, N*m/rad - coefficient of elasticity at upper boundary
1e6 N*m/rad (By default).
This parameter determines the degree of collision elasticity when the shaft reaches the upper bound. The larger the value of the parameter, the less the bodies penetrate each other, the harder the impact becomes. A smaller value of the parameter makes the contact softer, but generally improves convergence and computational efficiency.
Contact stiffness at lower bound, N*m/rad - coefficient of elasticity at lower boundary
1e6 N*m/rad (by default).
This parameter determines the degree of collision elasticity when the shaft reaches the upper boundary. The larger the value of the parameter, the less the bodies penetrate each other, the harder the impact becomes. A smaller value of the parameter makes the contact softer, but generally improves convergence and computational efficiency.
Contact damping at upper bound, N*m/(rad/s) - damping coefficient at upper boundary
0.01 N*m/(rad/s) (by default).
This parameter determines the collision damping when the shaft reaches the upper bound. The higher the value of the parameter, the more energy is dissipated during the interaction.
Contant damping at lower boundary, N*m/(rad/s) - damping coefficient at lower boundary
0.01 N*m/(rad/s) (by default).
This parameter determines the collision damping when the shaft reaches the lower bound. The higher the value of the parameter, the more energy is dissipated during the interaction.
Hard stop model - selection of the hard stop model
Stiffness and damping applied smoothly through transition region, damped rebound (by default) | Full stiffness and damping applied at bounds, undamped rebound | Full stiffness and damping applied at bounds, damped rebound.
Select a set of assumptions for block operation:
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`Stiffness and damping applied smoothly through transition region, damped rebound' - define a transition region in which the resistance torque builds up from zero. At the end of the transition region, full stiffness and damping is applied. In this model, rebound damping is applied, but it is limited by the value of the stiffness torque. In this sense, damping can reduce or eliminate the torque provided by stiffness, but never exceed it. All equations are smooth.
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Full stiffness and damping applied at bounds, undamped rebound- this model has full stiffness and damping applied at impact at upper and lower bounds, with no damping at rebound. The equations do not result in a zero crossing when the velocity changes sign, but there is a zero crossing at the boundaries based on position. The lack of rebound damping helps get the shaft out of this position quickly. This model has nonlinear equations. -
Full stiffness and damping applied at bounds, damped rebound- this model has full stiffness and damping applied at impact at upper and lower bounds, with damping applied at rebound too. The equations switch linearly, but result in a zero crossing based on position.
Transition region, rad - the region in which torque increases
0.001 rad (by default).
The region in which the torque increases from zero to the full value. At the end of the transition region, full stiffness and damping are applied.
Dependencies
Enabled when Hard stop model is set to `Stiffness and damping applied smoothly through transition region, damped rebound'.
Initial Targets
Initial value of rotational velocity, rad/s - initial value of rotational velocity
0.0 (by default)
Initial value of rotational velocity.
Initial value of torque, N*m - initial value of torque
0.0 (By default)
Initial value of torque.
Initial value of angular position, rad - initial value of angular position
0.0 (By default).
Initial value of angular position.