# SimpleHexapod¶

class lsst.ts.hexapod.SimpleHexapod(base_positions, mirror_positions, pivot, min_length, max_length, speed)

Bases: object

Simple model of a hexapod: 6 linear actuators in an arbitrary arrangement.

The intent is to support the mock hexapod controller; as such this model is somewhat simplistic. The actuators ends are assumed to be perfect point flexures. It is not (yet) possible to compute orientation given actuator lengths.

See make_zigzag_model to make a standard symmetrical zigzag hexapod.

Parameters: base_positions : List [List [float]] Position of the base end of each linear actuator, as a list of z,y,z tuples, one per actuator. mirror_positions : List [List [float]] Position of the mirror end of each actuator at zero orientation, as a list of z,y,z tuples, one per actuator. pivot : numpy.ndarray The point whose orientation is set by the move command. For a mirror it will typically be the vertex of the mirror. min_length : float Mininum actuator length. max_length : float Maximum actuator length. speed : float Actuator speed.

Methods Summary

 assert_in_range(actuator_lengths) Assert that all actuators would be in range if set to the specified length. compute_actuator_lengths(mirror_positions, …) Compute actuator lengths, given mirror positions. compute_mirror_positions(pos, xyzrot) Compute the actuator mirror positions needed to move the pivot point to a specified orientation. make_zigzag_model(base_radius, …) Make a SimpleHexapod of a typical hexapod with 6 actuators in a symmetrical zigzag arrangement. move(pos, xyzrot) Move the actuators so the pivot point is at the specified orientation. moving([tai]) Is any actuator moving? remaining_time([tai]) Remaining time for this move (sec). stop() Stop all actuators.

Methods Documentation

assert_in_range(actuator_lengths)

Assert that all actuators would be in range if set to the specified length.

compute_actuator_lengths(mirror_positions, absolute)

Compute actuator lengths, given mirror positions.

Parameters: mirror_positions : List [numpy.ndarray] Position of the mirror end of each actuator. absolute : bool If True then return end to end actuator lengths. If False then return lengths relative to neutral lengths; this requires self.neutral_actuator_lengths. actuator_end_to_end_lengths : numpy.ndarray End to end length of each actuator.
compute_mirror_positions(pos, xyzrot)

Compute the actuator mirror positions needed to move the pivot point to a specified orientation.

Parameters: pos : numpy.ndarray Desired x, y, z position of pivot point, relative to the neutral pivot point. xyzrot : numpy.ndarray Orientation of translated pivot point, as a rotation about x, then y, then z (deg). mirror_positions : List [numpy.ndarray] Resulting position of the mirror end of each actuator.
classmethod make_zigzag_model(base_radius, mirror_radius, mirror_z, base_angle0, pivot, min_length, max_length, speed)

Make a SimpleHexapod of a typical hexapod with 6 actuators in a symmetrical zigzag arrangement.

The base ends of the 6 actuators terminate at 3 points at z=0 evenly distributed about a circle of radius base_radius: actuators 0 and 5 terminate at base_angle0, actuators 1 and 2 terminate at base_angle0 + 120, and actuators 3 and 4 terminate at base_angle0 + 240. The mirror ends of the actuators are similarly arrayed, in a plane at z=mirror_z with attachment points rotated 60 degrees from the base attachment points: actuators 0 and 1 terminate at base_angle0 + 60, etc. This makes a zigzag pattern that is circularly symmetric about the z axis.

base_radius : float
Radius of base positions of actuators.
mirror_radius : float
Radius of mirror positions of actuators.
mirror_z : float
z distance between the base ends and the mirror ends of the linear actuators.
base_angle0 : float
Angle of first base actuator point in x,y plane (deg).
pivot : numpy.ndarray
The point whose orientation is set by the move command. For a mirror it will typically be the vertex of the mirror.
min_length : float
Mininum actuator length.
max_length : float
Maximum actuator length.
speed : float
Actuator speed.
move(pos, xyzrot)

Move the actuators so the pivot point is at the specified orientation.

Parameters: pos : numpy.ndarray x, y, z position of pivot point. xyzrot : numpy.ndarray Orientation of translated pivot point, as a rotation about x, then y, then z (deg). duration : float Duration of the move (second).
moving(tai=None)

Is any actuator moving?

remaining_time(tai=None)

Remaining time for this move (sec).

stop()

Stop all actuators.