Import upstream snapshot 57d13ead53206a6bf0db3d66f86506ae8c2ce01a

Upstream: https://github.com/pollen-robotics/bam Upstream-Commit: 57d13ead53206a6bf0db3d66f86506ae8c2ce01a Upstream-Branch: mjlab_frictionloss
2026-08-28 15:42:08 +08:00
commit 8be13016bc
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+# Copyright 2025 Marc Duclusaud & Grégoire Passault
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at:
+
+#     http://www.apache.org/licenses/LICENSE-2.0
+
+import numpy as np
+from bam.message import yellow, print_parameter, bright
+from bam.actuator import VoltageControlledActuator, CurrentControlledActuator
+from bam.parameter import Parameter
+from bam.testbench import Testbench, Pendulum
+
+
+class MXActuator(VoltageControlledActuator):
+    """
+    Represents a Dynamixel MX-64 or MX-106 actuator
+    """
+
+    def __init__(self, testbench_class: Testbench):
+        super().__init__(
+            testbench_class,
+            vin=15.0,
+            kp=32.0,
+            # This gain, if multiplied by a position error and firmware KP, gives duty cycle
+            # It was determined using an oscilloscope and MX actuators
+            error_gain=0.158,
+            # Maximum allowable duty cycle, also determined with oscilloscope
+            max_pwm=0.9625,
+        )
+
+    def initialize(self):
+        # Torque constant [Nm/A] or [V/(rad/s)]
+        self.model.kt = Parameter(1.6, 1.0, 3.0)
+
+        # Motor resistance [Ohm]
+        self.model.R = Parameter(2.0, 1.0, 5.0)
+
+        # Motor armature / apparent inertia [kg m^2]
+        self.model.armature = Parameter(0.005, 0.001, 0.05)
+
+    def get_extra_inertia(self) -> float:
+        return self.model.armature.value
+
+
+class XL320Actuator(VoltageControlledActuator):
+    """
+    Represents a Dynamixel XL-320 actuator
+    """
+
+    def __init__(self, testbench_class: Testbench):
+        super().__init__(
+            testbench_class,
+            vin=7.5,
+            kp=32.0,
+            # This gain, if multiplied by a position error and firmware KP, gives duty cycle
+            # It was determined using an oscilloscope and XL-320 actuators
+            error_gain=0.05048199,
+            # Maximum allowable duty cycle, also determined with oscilloscope
+            max_pwm=1.0,
+        )
+
+    def initialize(self):
+        # Torque constant [Nm/A] or [V/(rad/s)]
+        self.model.kt = Parameter(0.7, 0.25, 1.5)
+
+        # Motor resistance [Ohm]
+        self.model.R = Parameter(5.0, 3.0, 40.0)
+
+        # Motor armature / apparent inertia [kg m^2]
+        self.model.armature = Parameter(0.0005, 0.0001, 0.01)
+
+        self.model.max_load_friction = 1.0
+
+    def get_extra_inertia(self) -> float:
+        return self.model.armature.value
+
+
+XL330_ENCODER_COUNTS_PER_REV = 4096
+XL330_KP_DIVISOR = 256  # Empirically observed for XL330 (manual mentions 128)
+XL330_PWM_LIMIT = 885  # Default Present PWM limit for XL330
+
+
+class XL330Actuator(VoltageControlledActuator):
+    """
+    Represents a Dynamixel XL330 actuator.
+    """
+
+    def __init__(self, testbench_class: Testbench):
+        super().__init__(
+            testbench_class,
+            vin=7.5,
+            kp=400,
+            error_gain=(XL330_ENCODER_COUNTS_PER_REV / (2 * np.pi))
+            / (XL330_KP_DIVISOR * XL330_PWM_LIMIT),
+            max_pwm=1.0,
+            # Firmware current limit [A] for the XL330
+            max_current=1.75,
+        )
+
+    def initialize(self):
+        self.model.kt = Parameter(1.6, 0.1, 3.0)
+        self.model.R = Parameter(2.6, 2.0, 5.0)
+        self.model.armature = Parameter(0.005, 0.0001, 0.05)
+
+    def get_extra_inertia(self) -> float:
+        return self.model.armature.value
+
+
+class XL330CurrentActuator(CurrentControlledActuator):
+    """
+    Represents a Dynamixel XL330 actuator controlled in current position mode.
+    """
+
+    def __init__(self, testbench_class: Testbench):
+        super().__init__(
+            testbench_class,
+            vin=7.5,
+            kp=400,
+            error_gain=0.01,
+        )
+
+    def initialize(self):
+        self.model.kt = Parameter(1.6, 0.1, 3.0)
+        self.model.R = Parameter(2.6, 2.0, 5.0)
+        self.model.armature = Parameter(0.005, 0.0001, 0.05)
+        self.model.current_limit = Parameter(1.5, 1.0, 3.0)
+
+    def get_extra_inertia(self) -> float:
+        return self.model.armature.value