org.lsst.ccs.subsystems.shutter.sim

Class HallSensorSimulator

java.lang.Object

org.lsst.ccs.subsystems.shutter.sim.HallSensorSimulator

public class HallSensorSimulator
extends Object

Calculates when each Hall sensor undergoes a transition from open to closed and back to open.

Each instance of this class calculates a time-ordered set of Hall transitions for a single motion of a blade set. The transitions may be recovered as many times as needed by creating a stream from them.

Instances of this class are immutable.

This version of the class describes the old shutter test bench having a single blade set. The positions of Hall sensors and magnets is completely hard-coded. Use of a blade-set configuration is not yet implemented so the true positions of transitions in mm isn't available.

Hall sensor model:

• Relative blade set positions are used. See BladePosition.
• Each magnet and sensor occupies zero width along the track.
• There are nm magnets with spacing s mounted on the blade set, with the first magnet right on the edge.
• There are nh Hall sensors with spacing nm*s mounted along the track. Each sensor is sensitive to a magnet within a window of length w/2 on each side of the sensor. The window of the first sensor starts at offset woff from zero and the window of the last sensor ends at 1 - woff. w/2 is less than s.

When extending a blade set from the fully retracted position, the first transition pair begins when the edge reaches woff with one further transition pair every time it travels a further distance s. At the start of the last transition pair the last magnet will be just at the start of the window of the last sensor at position 1 - woff - w. The first magnet will therefore be at 1 - woff - w + (nm-1)*s and will have traveled a distance of 1 - woff - w + (nm-1)*s - woff since the start of the first transition pair. Since transition pairs are spaced at travel distance s the total distance traveled must also be (no. of transitions - 1)*s = (nm*nh - 1)*s. Then 1 - 2*woff -w +(nm-1)*s = (nm*nh-1)*s, or s = (1 - 2*woff - w) / (nm*(nh - 1)).

Parameters, currently hard coded:

• Nine magnets
• Four Hall sensors
• Sensor window offset = 0.0125
• Sensor window size = 0.00625
• Spacing between transition pairs = s = magnet spacing = 0.0359 (approx)
• Spacing between sensors = nm*s = 0.3229 (approx)

Since we know the position of the blade set's edge for every possible transition we just need to pick those positions that fall within the path traced by the edge. Then we can use the inverse position function of the motion profile to determine the time of each transition.

Author:

azemoon, tether

Constructor Summary

Constructors

Constructor and Description
HallSensorSimulator(long startTime, double startPosition, double endPosition, MotionProfile profile) Find all the Hall transitions relevant to the given motion of the blade set.

Method Summary

Modifier and Type	Method and Description
Stream<HallTransition>	getTransitions() Gets the time-ordered stream of Hall transitions.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

HallSensorSimulator

public HallSensorSimulator(long startTime,
                           double startPosition,
                           double endPosition,
                           MotionProfile profile)

Find all the Hall transitions relevant to the given motion of the blade set.

Parameters:

startTime - the starting time (a system time stamp in microseconds)

startPosition - the starting position of the blade set edge

endPosition - the ending position of the blade set edge

profile - the description of the physical motion

Method Detail

getTransitions

public Stream<HallTransition> getTransitions()

Gets the time-ordered stream of Hall transitions.

Returns:

the transition stream