Consolidate steerable interface into RollingDyadBot3D

Instead of a separate SteerableDyadBot3D, RollingDyadBot3D itself now has
individual torque inputs for the two wheels; models that drive both wheels
with the same torque (AngleControlledDyadBot3D) place the halving gain
outside the plant and connect it to both inputs. The x/x_dot outputs are
now odometric (average wheel arc length), which coincides with the
world-frame x coordinate when driving straight, so the planar-equivalence
test is unaffected.

Also add icons for ControlMixer and YawController, and make all diagram
placement boxes square since non-square components render poorly in the
GUI.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: baggepinnen

README.md

@@ -14,13 +14,11 @@ Plant models:
 - `DyadBot3D`: three-dimensional model with two individually spinning wheels
   with slip-based ground contact, allowing the body to tilt.
 - `RollingDyadBot3D`: three-dimensional model with an ideal no-slip rolling
-  wheel axle (`MultibodyComponents.RollingWheelSet`). Same interface and
-  parameters as `PlanarDyadBot`; for motion in the vertical plane it is
-  dynamically equivalent to the planar model.
-- `SteerableDyadBot3D`: like `RollingDyadBot3D` but with individually driven
+  wheel axle (`MultibodyComponents.RollingWheelSet`) and individually driven
   wheels, so the robot can be steered by differential torque. Outputs
   odometric path position/velocity, tilt angle/rate and yaw (heading)
-  angle/rate.
+  angle/rate. With equal torque on both wheels it is dynamically equivalent
+  to `PlanarDyadBot`.
 
 Closed-loop models around the planar plant:
 
@@ -41,7 +39,7 @@ Closed-loop models around the 3D plant:
   `AngleController` as `AngleControlledDyadBot`; with in-plane motion the
   closed-loop response is identical to the planar model
   (`test/test_stabilization.jl` verifies this).
-- `YawControlledDyadBot3D`: `SteerableDyadBot3D` with the balance/position
+- `YawControlledDyadBot3D`: `RollingDyadBot3D` with the balance/position
   cascade (`CascadeController`, position reference held at zero) and a
   separate `YawController` tracking a heading reference that steps at t = 5;
   a `ControlMixer` combines drive and yaw torque into the two wheel torque

assets/ControlMixer.svg

@@ -275,7 +275,7 @@ metadata {
       }
     },
     "zoh": {
-      "Dyad": {"placement": {"diagram": {"x1": 840, "y1": 450, "x2": 920, "y2": 550}}}
+      "Dyad": {"placement": {"diagram": {"x1": 830, "y1": 450, "x2": 930, "y2": 550}}}
     },
     "clock": {
       "Dyad": {"placement": {"diagram": {"x1": 410, "y1": 790, "x2": 510, "y2": 890}}}

assets/YawController.svg

@@ -242,6 +242,8 @@ component AngleControlledDyadBot3D
   world = MultibodyComponents.World(g = 9.82, nominal_length = 0.1) {^world}
   plant = RollingDyadBot3D(phi0 = phi0) {^plant}
   controller = AngleController(k_angle = k_angle, Ti_angle = Ti_angle, Td_angle = Td_angle) {^controller}
+  "Splits the motor torque equally between the two wheels"
+  gain_half = BlockComponents.Math.Gain(k = 0.5) {^gain_half}
   "Proportional gain of the angle controller"
   parameter k_angle::Real = 0.487401
   "Integrator time constant of the angle controller"
@@ -251,7 +253,8 @@ component AngleControlledDyadBot3D
   "Initial tilt angle of the body"
   parameter phi0::Angle = 0.1
 relations
-  connect(controller.torque, plant.torque) {^id4}
+  connect(controller.torque, gain_half.u) {^id4}
+  connect(gain_half.y, plant.torque_left, plant.torque_right) {^id6}
   connect(plant.theta, controller.measurement) {^id5}
 metadata {
   "Dyad": {
@@ -278,9 +281,18 @@ metadata {
     "controller": {
       "Dyad": {"placement": {"diagram": {"x1": 270, "y1": 420, "x2": 420, "y2": 570}}}
     },
-    "id4": {
+    "gain_half": {
+      "Dyad": {"placement": {"diagram": {"x1": 450, "y1": 455, "x2": 530, "y2": 535}}}
+    },
+    "id4": {"Dyad": {"edges": [{"S": 1, "M": [], "E": 2}]}},
+    "id6": {
       "Dyad": {
-        "edges": [{"S": 1, "M": [{"x": 503.75, "y": 495}, {"x": 503.75, "y": 500}], "E": 2}]
+        "edges": [
+          {"S": 1, "M": [], "E": -1},
+          {"S": -1, "M": [{"x": 545, "y": 460}], "E": 2},
+          {"S": 3, "M": [{"x": 545, "y": 530}], "E": -1}
+        ],
+        "junctions": [{"x": 545, "y": 495}]
       }
     },
     "id5": {
@@ -745,7 +757,7 @@ metadata {
       "Dyad": {"placement": {"diagram": {"x1": 60, "y1": 450, "x2": 160, "y2": 550}}}
     },
     "controller": {
-      "Dyad": {"placement": {"diagram": {"x1": 240, "y1": 410, "x2": 480, "y2": 600}}}
+      "Dyad": {"placement": {"diagram": {"x1": 265, "y1": 410, "x2": 455, "y2": 600}}}
     },
     "id7": {"Dyad": {"edges": [{"S": 1, "M": [], "E": 2}]}},
     "id8": {"Dyad": {"edges": [{"S": 1, "M": [], "E": 2}]}},
@@ -856,7 +868,7 @@ metadata {
       "Dyad": {"placement": {"diagram": {"x1": 120, "y1": 430, "x2": 220, "y2": 530}}}
     },
     "controller": {
-      "Dyad": {"placement": {"diagram": {"x1": 280, "y1": 390, "x2": 510, "y2": 570}}}
+      "Dyad": {"placement": {"diagram": {"x1": 305, "y1": 390, "x2": 485, "y2": 570}}}
     },
     "id7": {"Dyad": {"edges": [{"S": 1, "M": [], "E": 2}]}},
     "id8": {"Dyad": {"edges": [{"S": 1, "M": [], "E": 2}]}},

dyad/cascade_ff.dyad

@@ -288,7 +288,7 @@ metadata {
     "mux": {
       "Dyad": {
         "placement": {
-          "diagram": {"iconName": "default", "x1": 90, "y1": 450, "x2": 170, "y2": 550, "rot": 0}
+          "diagram": {"iconName": "default", "x1": 80, "y1": 450, "x2": 180, "y2": 550, "rot": 0}
         },
         "tags": []
       }