delta: Move "stable position" logic to delta_calibrate.py

Move the "stable position" logic from the delta.py kinematics code to
the delta_calibrate.py calibration code.

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

klippy/extras/delta_calibrate.py

@@ -3,9 +3,64 @@
 # Copyright (C) 2017-2018  Kevin O'Connor <kevin@koconnor.net>
 #
 # This file may be distributed under the terms of the GNU GPLv3 license.
-import math, logging
+import math, logging, collections
 import probe, mathutil
 
+
+######################################################################
+# Delta "stable position" coordinates
+######################################################################
+
+# A "stable position" is a 3-tuple containing the number of steps
+# taken since hitting the endstop on each delta tower.  Delta
+# calibration uses this coordinate system because it allows a position
+# to be described independent of the software parameters.
+
+# Storage helper for delta parameters
+DeltaParams = collections.namedtuple('DeltaParams', [
+    'radius', 'angles', 'arms', 'endstops', 'stepdists',
+    'towers', 'abs_endstops'])
+
+# Generate delta_params from delta configuration parameters
+def build_delta_params(params):
+    radius = params['radius']
+    angles = [params['angle_'+a] for a in 'abc']
+    arms = [params['arm_'+a] for a in 'abc']
+    endstops = [params['endstop_'+a] for a in 'abc']
+    stepdists = [params['stepdist_'+a] for a in 'abc']
+    # Calculate the XY cartesian coordinates of the delta towers
+    radian_angles = [math.radians(a) for a in angles]
+    towers = [(math.cos(a) * radius, math.sin(a) * radius)
+              for a in radian_angles]
+    # Calculate the absolute Z height of each tower endstop
+    radius2 = radius**2
+    abs_endstops = [e + math.sqrt(a**2 - radius2)
+                    for e, a in zip(endstops, arms)]
+    return DeltaParams(radius, angles, arms, endstops, stepdists,
+                       towers, abs_endstops)
+
+# Return cartesian coordinates for the given stable_positions when the
+# given delta_params are used.
+def get_position_from_stable(stable_position, delta_params):
+    dp = delta_params
+    sphere_coords = [
+        (t[0], t[1], es - sp * sd)
+        for sd, t, es, sp in zip(
+                dp.stepdists, dp.towers, dp.abs_endstops, stable_position) ]
+    return mathutil.trilateration(sphere_coords, [a**2 for a in dp.arms])
+
+# Return a stable position from the nominal delta tower positions
+def get_stable_position(stepper_position, delta_params):
+    dp = delta_params
+    return [int((ep - sp) / sd + .5)
+            for sd, ep, sp in zip(
+                    dp.stepdists, dp.abs_endstops, stepper_position)]
+
+
+######################################################################
+# Delta Calibrate class
+######################################################################
+
 class DeltaCalibrate:
     def __init__(self, config):
         self.printer = config.get_printer()
@@ -32,27 +87,34 @@ class DeltaCalibrate:
         self.probe_helper.start_probe()
     def get_probed_position(self):
         kin = self.printer.lookup_object('toolhead').get_kinematics()
-        return kin.get_stable_position()
+        return [s.get_commanded_position() for s in kin.get_steppers()]
     def finalize(self, offsets, positions):
         z_offset = offsets[2]
         kin = self.printer.lookup_object('toolhead').get_kinematics()
-        logging.info("Calculating delta_calibrate with: %s", positions)
         params = kin.get_calibrate_params()
-        logging.info("Initial delta_calibrate parameters: %s", params)
+        orig_delta_params = build_delta_params(params)
-        adj_params = ('endstop_a', 'endstop_b', 'endstop_c', 'radius',
+        stable_positions = [get_stable_position(p, orig_delta_params)
-                      'angle_a', 'angle_b')
+                            for p in positions]
+        logging.info("Calculating delta_calibrate with: %s\n"
+                     "Initial delta_calibrate parameters: %s",
+                     stable_positions, params)
+        adj_params = ('radius', 'angle_a', 'angle_b',
+                      'endstop_a', 'endstop_b', 'endstop_c')
         def delta_errorfunc(params):
+            delta_params = build_delta_params(params)
             total_error = 0.
-            for x, y, z in kin.get_positions_from_stable(positions, params):
+            for stable_pos in stable_positions:
+                x, y, z = get_position_from_stable(stable_pos, delta_params)
                 total_error += (z - z_offset)**2
             return total_error
         new_params = mathutil.coordinate_descent(
             adj_params, params, delta_errorfunc)
         logging.info("Calculated delta_calibrate parameters: %s", new_params)
-        old_positions = kin.get_positions_from_stable(positions, params)
+        new_delta_params = build_delta_params(new_params)
-        new_positions = kin.get_positions_from_stable(positions, new_params)
+        for spos in stable_positions:
-        for oldpos, newpos in zip(old_positions, new_positions):
+            logging.info("orig: %s new: %s",
-            logging.info("orig: %s new: %s", oldpos, newpos)
+                         get_position_from_stable(spos, orig_delta_params),
+                         get_position_from_stable(spos, new_delta_params))
         self.gcode.respond_info(
             "stepper_a: position_endstop: %.6f angle: %.6f\n"
             "stepper_b: position_endstop: %.6f angle: %.6f\n"

klippy/kinematics/delta.py

@@ -12,8 +12,7 @@ SLOW_RATIO = 3.
 class DeltaKinematics:
     def __init__(self, toolhead, config):
         # Setup tower rails
-        stepper_configs = [config.getsection('stepper_' + n)
+        stepper_configs = [config.getsection('stepper_' + a) for a in 'abc']
-                           for n in ['a', 'b', 'c']]
         rail_a = stepper.PrinterRail(
             stepper_configs[0], need_position_minmax = False)
         a_endstop = rail_a.get_homing_info().position_endstop
@@ -31,9 +30,9 @@ class DeltaKinematics:
             sconfig.getfloat('arm_length', arm_length_a, above=radius)
             for sconfig in stepper_configs]
         self.arm2 = [arm**2 for arm in arm_lengths]
-        self.endstops = [(rail.get_homing_info().position_endstop
+        self.abs_endstops = [(rail.get_homing_info().position_endstop
-                          + math.sqrt(arm2 - radius**2))
+                              + math.sqrt(arm2 - radius**2))
-                         for rail, arm2 in zip(self.rails, self.arm2)]
+                             for rail, arm2 in zip(self.rails, self.arm2)]
         # Setup boundary checks
         self.need_motor_enable = self.need_home = True
         self.limit_xy2 = -1.
@@ -41,7 +40,7 @@ class DeltaKinematics:
                           for rail in self.rails])
         self.min_z = config.getfloat('minimum_z_position', 0, maxval=self.max_z)
         self.limit_z = min([ep - arm
-                            for ep, arm in zip(self.endstops, arm_lengths)])
+                            for ep, arm in zip(self.abs_endstops, arm_lengths)])
         logging.info(
             "Delta max build height %.2fmm (radius tapered above %.2fmm)" % (
                 self.max_z, self.limit_z))
@@ -115,7 +114,7 @@ class DeltaKinematics:
                           homing_speed/2.0, second_home=True)
         # Set final homed position
         spos = [ep + rail.get_homed_offset()
-                for ep, rail in zip(self.endstops, self.rails)]
+                for ep, rail in zip(self.abs_endstops, self.rails)]
         homing_state.set_homed_position(self._actuator_to_cartesian(spos))
     def motor_off(self, print_time):
         self.limit_xy2 = -1.
@@ -160,38 +159,15 @@ class DeltaKinematics:
             self._check_motor_enable(print_time)
         for rail in self.rails:
             rail.step_itersolve(move.cmove)
-    # Helper functions for DELTA_CALIBRATE script
+    # Helper function for DELTA_CALIBRATE script
-    def get_stable_position(self):
-        steppers = [rail.get_steppers()[0] for rail in self.rails]
-        return [int((ep - s.get_commanded_position()) / s.get_step_dist() + .5)
-                for ep, s in zip(self.endstops, steppers)]
     def get_calibrate_params(self):
         out = { 'radius': self.radius }
         for i, axis in enumerate('abc'):
             rail = self.rails[i]
-            out['endstop_'+axis] = rail.get_homing_info().position_endstop
-            out['stepdist_'+axis] = rail.get_steppers()[0].get_step_dist()
             out['angle_'+axis] = self.angles[i]
             out['arm_'+axis] = self.arm_lengths[i]
-        return out
+            out['endstop_'+axis] = rail.get_homing_info().position_endstop
-    def get_positions_from_stable(self, stable_positions, params):
+            out['stepdist_'+axis] = rail.get_steppers()[0].get_step_dist()
-        angle_names = ['angle_a', 'angle_b', 'angle_c']
-        angles = [math.radians(params[an]) for an in angle_names]
-        radius = params['radius']
-        radius2 = radius**2
-        towers = [(math.cos(a) * radius, math.sin(a) * radius) for a in angles]
-        arm2 = [params[an]**2 for an in ['arm_a', 'arm_b', 'arm_c']]
-        stepdist_names = ['stepdist_a', 'stepdist_b', 'stepdist_c']
-        stepdists = [params[sn] for sn in stepdist_names]
-        endstop_names = ['endstop_a', 'endstop_b', 'endstop_c']
-        endstops = [params[en] + math.sqrt(a2 - radius2)
-                    for en, a2 in zip(endstop_names, arm2)]
-        out = []
-        for spos in stable_positions:
-            sphere_coords = [
-                (t[0], t[1], es - sp * sd)
-                for t, es, sd, sp in zip(towers, endstops, stepdists, spos) ]
-            out.append(mathutil.trilateration(sphere_coords, arm2))
         return out
 
 def load_kinematics(toolhead, config):