Acceleration and Deceleration Ramping

Acceleration The change in velocity as a function of time. and deceleration ramping lets the speed of the motion ramp cleanly between two different setpoints. The Automation1 controller uses acceleration The change in velocity as a function of time. and deceleration ramping when it creates the velocity profile for moves generated by MoveAbsolute(), MoveIncremental(), MoveFreerun(), MoveRapid(), MoveLinear(), MoveCw(), and MoveCcw(). The controller also uses acceleration The change in velocity as a function of time. and deceleration ramping during home moves and when it aborts moves.

Velocity Profile of a Move

When an axis is commanded to move, the controller generates a velocity profile, which is used to calculate position and velocity values at the time interval specified by the MotionUpdateRate Parameter and send these values to the position loop of the servo loop. The velocity profile usually includes the ramp segments that follow.

• Acceleration The change in velocity as a function of time. segment - the portion of the velocity profile in which the velocity ramps between the starting velocity and the target velocity.
• Constant velocity segment - the portion of the velocity profile during which the velocity stays at the target velocity.
• Deceleration segment - the portion of the velocity profile in which the velocity ramps between the target velocity and the ending velocity.

Figure: Acceleration The change in velocity as a function of time. and Deceleration

Ramp Types

The Automation1 controller lets you select one of three different ramp types to use when you generate a velocity profile for a move.

• Linear
• Sinusoidal (Half-Sine)
• S-Curve

Figure: Linear, Half-Sine, and S-curve Ramping

For each ramp type, the ramp rate that you specify is the average acceleration The change in velocity as a function of time. value of the full ramp. Thus, different ramp types have different peak accelerations, as in the above figure.

Linear Ramp Type

For a linear ramp, the controller uses a constant acceleration The change in velocity as a function of time. value, the configured ramp rate, to ramp the velocity from one setpoint to another. A linear ramp has these properties:

• The peak acceleration The change in velocity as a function of time. value is equal to the average acceleration The change in velocity as a function of time. value throughout the ramp.
• This type of ramping causes the lowest possible peak acceleration The change in velocity as a function of time..
• The ramp immediately gets to peak acceleration The change in velocity as a function of time..
• High jerk values can occur at the ramp boundaries.

To set the ramp type to Linear, specify the Linear ramp type in the SetupCoordinatedRampType() function.

SetupCoordinatedRampType(RampType.Linear)

Sinusoidal (Half-Sine) Ramp Type

A half-sine ramp type uses an acceleration The change in velocity as a function of time. value that follows a half-cycle of a sine wave whose amplitude is set so that the average value across the ramp is equal to the configured ramp rate. A half-sine ramp has these properties:

• The peak acceleration The change in velocity as a function of time. value is 1.57 times the average acceleration The change in velocity as a function of time. value.
• This type of ramping causes higher peak accelerations than the linear ramp type.
• The ramp gradually gets to peak acceleration The change in velocity as a function of time..
• Jerk values are lower than those of the linear ramp type.

To set the ramp type to Sinusoidal, specify the Sine ramp type in the SetupCoordinatedRampType() function.

SetupCoordinatedRampType(RampType.Sine)

S-Curve Ramp Type

An S-Curve ramp type uses a percentage value to find how much of the acceleration The change in velocity as a function of time. ramp is non-constant acceleration The change in velocity as a function of time..

Figure: Velocity Profile - S-CURVE 50

During the curved portions of the acceleration The change in velocity as a function of time. ramp, the jerk is constant. A larger S-Curve percentage causes a lower constant jerk value.

An S-Curve ramp with 0% curvature is the same as a Linear ramp and has a peak acceleration The change in velocity as a function of time. of 1.0 times the average acceleration The change in velocity as a function of time.. An S-Curve ramp with 100% curvature has a peak acceleration The change in velocity as a function of time. of 2.0 times the average acceleration The change in velocity as a function of time..

An S-Curve ramp has these properties:

• The peak acceleration The change in velocity as a function of time. value is 2.0 times the average acceleration The change in velocity as a function of time. value at the maximum curvature percentage.
• This type of ramping causes higher peak accelerations than the linear ramp type.
• The ramp gradually gets to peak acceleration The change in velocity as a function of time..
• The S-Curve percentage supplies some control over how high the jerk value will be.

To set the ramp type to S-Curve, specify the SCurve ramp type and the curvature percentage that you want in the SetupCoordinatedRampType() function.

SetupCoordinatedRampType(RampType.SCurve, 50.0)

Ramp Modes

The Automation1 controller supports two ramp modes:

• Rate-based ramping
• Time-based ramping

These modes affect how the controller generates acceleration The change in velocity as a function of time. and deceleration ramps.

SetupCoordinatedRampValue(RampMode.Rate, 2000.0)

SetupCoordinatedRampValue(RampMode.Time, 0.5)		

Ramping Commands and Parameters

The Automation1 controller supplies AeroScript API functions and controller parameters to configure the ramping behavior.