winch: Add experimental support for cable winch kinematics

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/kinematics/winch.py

@@ -0,0 +1,62 @@
+# Code for handling the kinematics of cable winch robots
+#
+# Copyright (C) 2018  Kevin O'Connor <kevin@koconnor.net>
+#
+# This file may be distributed under the terms of the GNU GPLv3 license.
+import stepper, mathutil
+
+class WinchKinematics:
+    def __init__(self, toolhead, config):
+        # Setup steppers at each anchor
+        self.steppers = []
+        self.anchors = []
+        for i in range(26):
+            name = 'stepper_' + chr(ord('a') + i)
+            if i >= 3 and not config.has_section(name):
+                break
+            stepper_config = config.getsection(name)
+            s = stepper.PrinterStepper(stepper_config)
+            self.steppers.append(s)
+            a = tuple([stepper_config.getfloat('anchor_' + n) for n in 'xyz'])
+            self.anchors.append(a)
+            s.setup_itersolve('winch_stepper_alloc', *a)
+        # Setup stepper max halt velocity
+        max_velocity, max_accel = toolhead.get_max_velocity()
+        max_halt_velocity = toolhead.get_max_axis_halt()
+        for s in self.steppers:
+            s.set_max_jerk(max_halt_velocity, max_accel)
+        # Setup boundary checks
+        self.need_motor_enable = True
+        self.set_position([0., 0., 0.], ())
+    def get_steppers(self, flags=""):
+        return list(self.steppers)
+    def calc_position(self):
+        # Use only first three steppers to calculate cartesian position
+        spos = [s.get_commanded_position() for s in self.steppers[:3]]
+        return mathutil.trilateration(self.anchors[:3], [sp*sp for sp in spos])
+    def set_position(self, newpos, homing_axes):
+        for s in self.steppers:
+            s.set_position(newpos)
+    def home(self, homing_state):
+        # XXX - homing not implemented
+        homing_state.set_axes([0, 1, 2])
+        homing_state.set_homed_position([0., 0., 0.])
+    def motor_off(self, print_time):
+        for s in self.steppers:
+            s.motor_enable(print_time, 0)
+        self.need_motor_enable = True
+    def _check_motor_enable(self, print_time):
+        for s in self.steppers:
+            s.motor_enable(print_time, 1)
+        self.need_motor_enable = False
+    def check_move(self, move):
+        # XXX - boundary checks and speed limits not implemented
+        pass
+    def move(self, print_time, move):
+        if self.need_motor_enable:
+            self._check_motor_enable(print_time)
+        for s in self.steppers:
+            s.step_itersolve(move.cmove)
+
+def load_kinematics(toolhead, config):
+    return WinchKinematics(toolhead, config)