Trajectory interpolator¶

This chapter describes the TrajectoryInterpolator interface. It represents an entity which interpolates the trajectory calculated by the trajectory generator and determines the setpoint values for each sample.

State machine¶

Each trajectory follows the profile displayed in figure Trajectory states. The trajectory states are described in table Trajectory states.

Trajectory states¶

Trajectory states¶
Trajectory state	Description
InPosition	DemandPosition does not change
Accelerating	The absolute value of DemandVelocity is increasing
ConstantVelocity	DemandVelocity is constant and unequal to zero
Decelerating	The absolute value of DemandVelocity is decreasing
QuickStop	The trajectory interpolator gives setpoints belonging to a second order trajectory with zero end velocity and minimum distance, while satisfying the QuickstopDeceleration constraint

TrajectoryState

C++

ETrajectoryState

Signals¶

Signals present for all trajectory interpolator types are listed in table Generic trajectory interpolator signals.

Generic trajectory interpolator signals¶
Name	Data type	R/W	Description
DemandAcceleration	Float	R	Acceleration setpoint calculated by trajectory interpolator.
DemandAccelerationLimit	Float	RW	Maximum allowed demand acceleration. Zero disables the protection.
DemandJerk	Float	R	Jerk setpoint calculated by trajectory interpolator.
DemandJerkLimit	Float	RW	Maximum allowed demand jerk. Zero disables the protection.
DemandPosition	Double	R	Position setpoint calculated by trajectory interpolator.
DemandPositionHighLimit	Double	RW	Demand position high limit for software end-switch determination. DemandPositionLowLimit \(\ge\) DemandPositionHighLimit disables the protection.
DemandPositionLowLimit	Double	RW	Demand position low limit for software end-switch determination. DemandPositionLowLimit \(\ge\) DemandPositionHighLimit disables the protection.
DemandVelocity	Float	R	Velocity setpoint calculated by trajectory interpolator.
DemandVelocityLimit	Float	RW	Maximum allowed demand velocity. Zero disables the protection.
RemainingMoveTime	Float	R	Remaining move time for current trajectory. While the trajectory is being calculated: + Infinity.
TargetPosition	Double	R	Target position for the current trajectory (or last when InPosition) Phase 1: until TrajectoryComplete Absolute position moves: provided end position Relative position moves: calculated using provided distance Jog moves: calculated position when velocity reached Smooth- and quickstop moves: calculated end position Phase 2: at TrajectoryComplete and after Position moves with non-zero end-velocity: ± Infinity Jog moves with non-zero velocity: ± Infinity Otherwise: no change
TargetVelocity	Float	R	Target velocity for the current trajectory (or last when InPosition) Position moves: provided end-velocity Jog moves: provided velocity

Events¶

The trajectory interpolator has the following events:

In position.
Trajectory complete.

In position¶

The in position event is generated when the trajectory state is InPosition.

Trajectory complete¶

The trajectory complete event is generated when the trajectory state is InPosition for move commands without end velocity, or upon the final transition to trajectory state ConstantVelocity for move commands with end velocity.