Changed Motor.PIDSetting to match.

Charles Weir · Charles Weir · commit e31c5093cb02 · 2014-03-14T21:50:27.000Z
diff --git a/BrickPython/Motor.py b/BrickPython/Motor.py
@@ -11,14 +11,14 @@ class PIDSetting():
     Distances are in clicks, times in ms, motor power between -255 and +255, the sum of distance is added 20 times/sec.
     Speeds in clicks per second.
     '''
-    def __init__(self,distanceMultiplier=0.9,speedMultiplier=0.23,sumDistanceMultiplier=0.05,
+    def __init__(self,distanceMultiplier=0.9,speedMultiplier=0.23,integratedDistanceMultiplier=(0.05/20.0),
                  closeEnoughPosition=4, closeEnoughSpeed=10.0):
-        #: Factor for motor power as function of distance.
+        #: Factor for motor power as function of distance - in power units per click distance.
         self.distanceMultiplier = distanceMultiplier
-        #: Factor for motor power as function of speed.
+        #: Factor for motor power as function of speed - in power units per (click per millisecond)
         self.speedMultiplier = speedMultiplier
-        #: Factor for motor power as function of sum of distances.
-        self.sumDistanceMultiplier = sumDistanceMultiplier
+        #: Factor for motor power as a function of the integrated distance - in power units per (click-millisecond)
+        self.integratedDistanceMultiplier = integratedDistanceMultiplier
         #: Distance in clicks from the target that we'll accept as got there.
         self.closeEnoughPosition = closeEnoughPosition
         #: Speed that we'll consider as close enough to zero.
@@ -138,7 +138,7 @@ def positionUsingPIDAlgorithmWithoutTimeout( self, target ):
 
                 power = (self.pidSetting.distanceMultiplier * delta
                          - self.pidSetting.speedMultiplier * speed
-                         + self.pidSetting.sumDistanceMultiplier * distanceIntegratedOverTime )
+                         + self.pidSetting.integratedDistanceMultiplier * distanceIntegratedOverTime )
                 self.setPower( power )
 
                 yield
diff --git a/CHANGES.txt b/CHANGES.txt
@@ -1,5 +1,10 @@
 # BrickPython Changelog
 
+## BrickPython v.4
+
+- Updated PID algorithm so it's independent of the work cycle time.  NOTE: One parameter to the constructor of
+  Motor.PIDSetting has changed.
+
 ## BrickPython v0.3.1
 
 - Reduced sampling frequency so TkWindow shows correctly.
diff --git a/ExamplePrograms/MotorController.py b/ExamplePrograms/MotorController.py
@@ -71,9 +71,9 @@ def onKeyPress(self, event):
             elif char == 'Y':
                 self.pidSetting.speedMultiplier /= 1.1
             elif char == 'z':
-                self.pidSetting.sumDistanceMultiplier *= 1.1
+                self.pidSetting.integratedDistanceMultiplier *= 1.1
             elif char == 'Z':
-                self.pidSetting.sumDistanceMultiplier /= 1.1
+                self.pidSetting.integratedDistanceMultiplier /= 1.1
             logging.info( "%r" % (self.pidSetting) )
             self.motor('A').setPIDSetting( self.pidSetting )
 
diff --git a/test/TestMotor.py b/test/TestMotor.py
@@ -106,6 +106,8 @@ def testPowerIsFunctionOfSumDistance(self):
         motor = self.motor
         # When the motor isn't moving and is some distance from the target
         co = motor.positionUsingPIDAlgorithmWithoutTimeout( 100 )
+        # And we have quite long work cycles:
+        motor.timeMillis.side_effect = range(0,990,20)
         # The motor power increases with time
         motor.updatePosition( 0 )
         co.next()
@@ -116,10 +118,10 @@ def testPowerIsFunctionOfSumDistance(self):
         self.assertGreater( p2, p1 )
 
         # And the motor power depends on time between readings, so if we do it all again
-        # with with longer between readings and a different motor
+        # with with longer work cycles and a different motor
         motorB = self.bp.motor( 'B' )
         motorB.timeMillis = Mock()
-        motorB.timeMillis.side_effect = range(0,99,2)
+        motorB.timeMillis.side_effect = range(0,990,40)
         co = motorB.positionUsingPIDAlgorithmWithoutTimeout( 100 )
         motorB.updatePosition( 0 )
         co.next()
