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fix(actuators): read an actuator's phase from the position it is put in - #63
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An ArcCrank kept its angle and sweep direction, a LinearActuator its extension and direction, and a Mechanism DriverLink / ArcDriverLink its current_angle, as internal state that set_coords() left alone; only a Crank reads its angle from its coordinates. So the second evaluation of a candidate by kinematic_minimization, a sensitivity analysis or a simulation() context started with the actuator wherever the previous run had stopped it, and two evaluations of the same candidate returned different loci. ArcCrank.set_coord() and LinearActuator.set_coord() now read the angle or the extension from the position they are given — the angle brought onto the arc, since an arc can reach past the range of atan2, the extension held within the stroke — and restart the sweep in the positive direction, as a new actuator does. reload() writes x and y directly, so it is unaffected. Mechanism.set_joint_positions(), hence set_coords(), rebuild() and set_completely(), calls the new DriverLink.read_angle() / ArcDriverLink.read_angle(), which do the same from the motor and output joints. Noted in the review of #62.
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The pre-existing limitation noted in the review of #62.
set_coords()put the joints back but not the actuators: anArcCrankkept_angle/_direction, aLinearActuator_extension/_direction, aMechanismDriverLink/ArcDriverLinkitscurrent_angle. Only aCrankre-derives its angle from x/y. So in an optimizer, a sensitivity analysis or asimulation()context, each run started with the actuator wherever the previous one had stopped it — two evaluations of the same candidate returned different loci.Fix: coordinates are now the whole state, for every actuator, as they already were for
Crank.ArcCrank.set_coord()reads the angle from the anchor→position direction, brought onto the arc (an arc like[0, 3π/2]reaches pastatan2's range; off the arc, the nearer end), and restarts the sweep forward as a new crank does.reload()writesx/ydirectly, so stepping is unaffected.LinearActuator.set_coord()reads the extension as the projection onto its axis, held within[0, stroke], and restarts extending.DriverLink.read_angle()/ArcDriverLink.read_angle()do the same from the motor and output joints;Mechanism.set_joint_positions()— henceset_coords(),rebuild(),set_completely()— calls them.Tests: repeated
kinematic_default_testevaluations give identical loci forCrank,ArcCrankandLinearActuator(and equal a fresh linkage's run);Mechanismruns repeat afterset_coords; unit tests for eachset_coord/read_angleincluding the arc wrap-around and the unplaced-joint case. 11 of them fail onmain. Full suite (2650) and docs tests green. Also drops the now-stale "cannot be rewound" wording from #62's comment and changelog.__all__untouched:read_angleis a method, the arc helper is private ingeometry.core.