try mujoco
This commit is contained in:
LiuzhengSJ
@ -1,6 +1,7 @@
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#!/usr/bin/env python3
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"""
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Simple Position Control with Velocity and Acceleration Limits - WITH IMPROVED CONVERGENCE
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Pure Position Control for MuJoCo - No velocity commands, no forces
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Direct joint position control with smoothing
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"""
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import mujoco
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@ -11,24 +12,25 @@ import time
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from pathlib import Path
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class SimplePositionController:
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class MuJoCoPositionController:
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"""
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Simple position control with velocity and acceleration limits
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Pure position control - directly sets joint positions
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No velocity commands, no forces - completely stable
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"""
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def __init__(self, urdf_path,
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max_velocity=2.0, # rad/s
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max_acceleration=5.0, # rad/s²
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control_dt=0.01, # seconds
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enable_viewer=True):
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def __init__(self, urdf_path, smoothness=0.05, enable_viewer=True):
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"""
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Args:
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urdf_path: Path to URDF file
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smoothness: Motion smoothness (0.02=very smooth, 0.1=fast)
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enable_viewer: Show MuJoCo viewer
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"""
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# Load model
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self.model = mujoco.MjModel.from_xml_path(urdf_path)
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self.data = mujoco.MjData(self.model)
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# Robot info
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self.n_joints = self.model.njnt
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self.control_dt = control_dt
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# Get joint limits
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self.joint_lower_limits = []
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@ -38,28 +40,20 @@ class SimplePositionController:
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self.joint_upper_limits.append(self.model.jnt_range[i, 1])
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print(f"Loaded robot: {self.n_joints} joints")
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print(f"Velocity limit: {max_velocity} rad/s")
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print(f"Acceleration limit: {max_acceleration} rad/s²")
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for i in range(self.n_joints):
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print(
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f" {self.model.joint(i).name}: limit [{self.joint_lower_limits[i]:.2f}, {self.joint_upper_limits[i]:.2f}]")
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# Control limits
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self.max_vel = max_velocity
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self.max_acc = max_acceleration
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# Target and current positions
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# Target positions (in radians)
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self.target_positions = self.data.qpos[:self.n_joints].copy()
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self.current_positions = self.data.qpos[:self.n_joints].copy()
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# For motion limiting
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self.current_command = self.data.qpos[:self.n_joints].copy()
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self.previous_command = self.data.qpos[:self.n_joints].copy()
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# For convergence zone - slow down when close to target
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self.slow_zone_radius = 0.2 # rad - start slowing down within this distance
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self.slow_zone_velocity = 0.3 # rad/s - max velocity in slow zone
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# Smoothing factor (0-1, lower = smoother)
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self.smoothness = smoothness
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# Thread safety
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self.command_lock = threading.Lock()
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self.feedback_lock = threading.Lock()
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self.current_feedback = self.data.qpos[:self.n_joints].copy()
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# Control flags
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self.running = False
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@ -74,19 +68,20 @@ class SimplePositionController:
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except Exception as e:
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print(f"Viewer warning: {e}")
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print("Controller ready\n")
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print("Robot controller ready - Pure Position Mode")
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def start(self):
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"""Start simulation thread"""
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"""Start the simulation thread"""
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if self.running:
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return
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self.running = True
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self.simulation_thread = threading.Thread(target=self._simulation_loop, daemon=True)
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self.simulation_thread.start()
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print("Simulation started")
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print("Simulation thread started")
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def stop(self):
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"""Stop simulation"""
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"""Stop the simulation thread"""
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self.running = False
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if self.simulation_thread:
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self.simulation_thread.join(timeout=2.0)
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@ -95,7 +90,12 @@ class SimplePositionController:
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print("Simulation stopped")
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def send_command(self, joint_positions):
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"""Send target joint positions"""
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"""
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Send target joint positions
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Args:
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joint_positions: Array of target joint angles (radians)
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"""
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cmd = np.array(joint_positions[:self.n_joints], dtype=np.float64)
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# Apply joint limits
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@ -108,87 +108,112 @@ class SimplePositionController:
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def get_feedback(self):
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"""Get current joint positions"""
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with self.feedback_lock:
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return self.current_positions.copy()
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return self.current_feedback.copy()
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def get_target(self):
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"""Get current target positions"""
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with self.command_lock:
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return self.target_positions.copy()
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def _simulation_loop(self):
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"""Main simulation loop"""
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"""
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Main simulation loop - PURE POSITION CONTROL
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No velocity commands, no forces - just direct position setting
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"""
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last_time = time.time()
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# For smooth interpolation
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current_positions = self.data.qpos[:self.n_joints].copy()
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while self.running:
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# Get target
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# Get target command
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with self.command_lock:
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target = self.target_positions.copy()
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# Calculate distance to target
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distance_to_target = target - self.current_command
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# Get current positions
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current_positions = self.data.qpos[:self.n_joints].copy()
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# Adaptive velocity based on distance (slow down when close)
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for i in range(self.n_joints):
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dist = abs(distance_to_target[i])
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if dist < self.slow_zone_radius:
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# Slow down proportionally to distance
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max_vel_for_joint = self.slow_zone_velocity * (dist / self.slow_zone_radius)
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max_vel_for_joint = max(max_vel_for_joint, 0.05) # Minimum velocity
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else:
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max_vel_for_joint = self.max_vel
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# Smooth interpolation toward target
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# This creates natural motion without velocity commands
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alpha = self.smoothness
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# Limit the step size
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max_step = max_vel_for_joint * self.control_dt
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if abs(distance_to_target[i]) > max_step:
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distance_to_target[i] = np.sign(distance_to_target[i]) * max_step
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delt_pos = np.clip( (target - current_positions), -0.02, 0.02)
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next_positions = current_positions + alpha * delt_pos
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# Apply acceleration limit
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delta = distance_to_target
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current_vel = (self.current_command - self.previous_command) / self.control_dt
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desired_vel = delta / self.control_dt
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max_vel_change = self.max_acc * self.control_dt
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# DIRECT POSITION CONTROL - Set joint positions
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self.data.qpos[:self.n_joints] = next_positions
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vel_diff = desired_vel - current_vel
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if np.any(np.abs(vel_diff) > max_vel_change):
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vel_diff = np.clip(vel_diff, -max_vel_change, max_vel_change)
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delta = (current_vel + vel_diff) * self.control_dt
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# Update command
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next_command = self.current_command + delta
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# Store for next iteration
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self.previous_command = self.current_command.copy()
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self.current_command = next_command.copy()
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# Direct position control
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self.data.qpos[:self.n_joints] = next_command
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# IMPORTANT: Set velocities to zero to prevent physics from moving joints
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# This ensures pure kinematic control
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self.data.qvel[:self.n_joints] = 0
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# Step physics
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# Step physics (this will apply gravity, collisions, etc. to other bodies)
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mujoco.mj_step(self.model, self.data)
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# Maintain position (physics might change it)
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self.data.qpos[:self.n_joints] = next_command
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# After step, ensure our joint positions are maintained
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# (Physics might have altered them slightly)
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self.data.qpos[:self.n_joints] = next_positions
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self.data.qvel[:self.n_joints] = 0
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# Update feedback
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with self.feedback_lock:
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self.current_positions = self.data.qpos[:self.n_joints].copy()
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self.current_feedback = self.data.qpos[:self.n_joints].copy()
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# Sync viewer
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if self.viewer:
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self.viewer.sync()
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# Maintain control rate
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# Maintain real-time speed
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elapsed = time.time() - last_time
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sleep_time = self.control_dt - elapsed
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sleep_time = self.model.opt.timestep - elapsed
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if sleep_time > 0:
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time.sleep(sleep_time)
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last_time = time.time()
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def wait_for_convergence(self, tolerance=0.01, timeout=2.0):
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"""Wait for robot to converge to target"""
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def move_to_position(self, target, duration=1.0):
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"""
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Move to target position over specified duration
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Args:
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target: Target joint positions
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duration: Time to complete movement (seconds)
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"""
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start_pos = self.get_feedback()
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end_pos = np.array(target[:self.n_joints])
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# Apply limits
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for i in range(self.n_joints):
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end_pos[i] = np.clip(end_pos[i], self.joint_lower_limits[i], self.joint_upper_limits[i])
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n_steps = int(duration / self.model.opt.timestep)
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print(f" Moving over {duration}s ({n_steps} steps)")
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for step in range(n_steps):
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alpha = (step + 1) / n_steps
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# Use easing for smoother motion
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ease_alpha = 1 - (1 - alpha) ** 2 # Quadratic ease-out
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current_target = start_pos + ease_alpha * (end_pos - start_pos)
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self.send_command(current_target)
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time.sleep(self.model.opt.timestep)
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# Ensure exact target
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self.send_command(end_pos)
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time.sleep(0.1)
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def wait_until_reached(self, tolerance=0.01, timeout=5.0):
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"""
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Wait until robot reaches target position
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Args:
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tolerance: Position error tolerance (radians)
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timeout: Maximum wait time (seconds)
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"""
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start_time = time.time()
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while time.time() - start_time < timeout:
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current = self.get_feedback()
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with self.command_lock:
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target = self.target_positions
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target = self.get_target()
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error = np.max(np.abs(target - current))
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if error < tolerance:
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@ -198,57 +223,69 @@ class SimplePositionController:
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return False
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def print_state(self):
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"""Print current robot state"""
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positions = self.get_feedback()
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target = self.get_target()
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print("Current positions:", [f"{p:.3f}" for p in positions[:4]], "...")
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print("Target positions: ", [f"{t:.3f}" for t in target[:4]], "...")
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# Demo
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def demo_position_control():
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"""Demonstrate pure position control"""
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def simple_test():
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"""Test with improved convergence"""
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urdf_path = "/home/zl/Downloads/urdf_rm75/RM75-B.urdf"
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robot = SimplePositionController(
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urdf_path,
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max_velocity=2.0, # 2 rad/s
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max_acceleration=5.0,
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control_dt=0.01,
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enable_viewer=True
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)
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if not Path(urdf_path).exists():
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print(f"Error: URDF not found at {urdf_path}")
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return
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print("=" * 60)
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print("Pure Position Control Demo")
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print("=" * 60)
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# Create controller
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robot = MuJoCoPositionController(urdf_path, smoothness=0.05, enable_viewer=True)
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robot.start()
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time.sleep(1)
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print("\n[Test 1] Move joint 1 to 45 degrees")
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robot.send_command([0.785, 0, 0, 0, 0, 0, 0])
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robot.wait_until_reached()
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robot.print_state()
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time.sleep(0.5)
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print("\n[Test 2] Move joint 2 to -30 degrees")
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robot.send_command([0, -0.524, 0, 0, 0, 0, 0])
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robot.wait_until_reached()
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robot.print_state()
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time.sleep(0.5)
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print("\n[Test 3] Move multiple joints simultaneously")
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robot.send_command([0.5, -0.4, 0.3, 0.2, 0.1, 0, 0])
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robot.wait_until_reached()
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robot.print_state()
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time.sleep(0.5)
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print("\n[Test 4] Return home")
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robot.send_command([0, 0, 0, 0, 0, 0, 0])
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robot.wait_until_reached()
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robot.print_state()
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print("\n[Test 5] Smooth trajectory using move_to_position")
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robot.move_to_position([0.6, -0.5, 0.4, 0.2, 0, 0, 0], duration=2.0)
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robot.wait_until_reached()
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robot.print_state()
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print("\n[Test 6] Back home with smooth motion")
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robot.move_to_position([0, 0, 0, 0, 0, 0, 0], duration=2.0)
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robot.wait_until_reached()
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robot.print_state()
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print("\n" + "=" * 60)
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print("Testing movement with smooth convergence")
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print("✓ All tests passed! Robot is stable and controllable.")
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print("=" * 60)
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# Test 1: Move to 0.8 rad and back
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print("\n[Test 1] Moving to +0.8 rad")
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robot.send_command([0.8, 0, 0, 0, 0, 0, 0])
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robot.wait_for_convergence(tolerance=0.01)
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pos = robot.get_feedback()
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print(f" Converged to: {pos[0]:.4f} rad (error: {abs(pos[0] - 0.8):.4f})")
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print("\n[Test 2] Moving to -0.8 rad")
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robot.send_command([-0.8, 0, 0, 0, 0, 0, 0])
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robot.wait_for_convergence(tolerance=0.01)
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pos = robot.get_feedback()
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print(f" Converged to: {pos[0]:.4f} rad (error: {abs(pos[0] + 0.8):.4f})")
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print("\n[Test 3] Moving to home (0 rad)")
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robot.send_command([0, 0, 0, 0, 0, 0, 0])
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robot.wait_for_convergence(tolerance=0.01)
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pos = robot.get_feedback()
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print(f" Converged to: {pos[0]:.4f} rad (error: {abs(pos[0]):.4f})")
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print("\n[Test 4] Multi-joint movement")
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robot.send_command([0.5, -0.3, 0.2, 0.1, 0, 0, 0])
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robot.wait_for_convergence(tolerance=0.01)
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pos = robot.get_feedback()
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print(f" Final positions: {[f'{p:.3f}' for p in pos[:4]]}...")
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print("\n[Test 5] Return home")
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robot.send_command([0, 0, 0, 0, 0, 0, 0])
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robot.wait_for_convergence(tolerance=0.01)
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pos = robot.get_feedback()
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print(f" Home positions: {[f'{p:.3f}' for p in pos[:4]]}...")
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print("\n✓ All tests passed! Robot converges quickly to target.")
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print("\nInteractive mode - close viewer to exit")
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try:
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@ -260,50 +297,43 @@ def simple_test():
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robot.stop()
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def back_and_forth_test():
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"""Back and forth test showing smooth convergence"""
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# Simple usage for your kinematic code
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def example_for_kinematic_code():
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"""Example of how to use with your kinematic solver"""
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urdf_path = "/home/zl/Downloads/urdf_rm75/RM75-B.urdf"
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robot = SimplePositionController(
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urdf_path,
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max_velocity=2.0,
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max_acceleration=5.0,
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control_dt=0.01,
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enable_viewer=True
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)
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robot = MuJoCoPositionController(urdf_path, smoothness=0.05, enable_viewer=True)
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robot.start()
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time.sleep(1)
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print("\n" + "=" * 60)
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print("Back and forth movement with smooth convergence")
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print("=" * 60)
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# Your kinematic solver would compute joint targets like this:
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def your_kinematic_solver(target_pose):
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"""
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Your kinematic code here
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Returns joint positions array of length 7
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"""
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# Example output - replace with your actual kinematics
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return np.array([0.5, -0.3, 0.2, 0.1, 0, 0, 0])
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targets = [[0, -0.524, 0, 0, 0, 0, 0],
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[0.5, -0.4, 0.3, 0.2, 0.1, 0, 0],
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[0.6, -0.5, 0.4, 0.2, 0, 0, 0],
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[0, 0, 0, 0, 0, 0, 0]
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]
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# Example usage
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target_pose = "some pose" # Your pose input
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for target in targets:
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print(f"\nMoving to {target} rad...")
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start_time = time.time()
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# Compute joint targets using your kinematics
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joint_targets = your_kinematic_solver(target_pose)
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robot.send_command(target)
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# Send to simulation
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robot.send_command(joint_targets)
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# Wait for convergence
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robot.wait_for_convergence(tolerance=0.01, timeout=2.0)
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# Wait for robot to reach target
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robot.wait_until_reached()
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elapsed = time.time() - start_time
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pos = robot.get_feedback()
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error = sum( abs( np.array(pos) - np.array(target) ) )
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# Read actual positions
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actual_positions = robot.get_feedback()
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|
||||
print(f" Position: {pos[0]:.4f} rad, Error: {error:.4f} rad, Time: {elapsed:.2f}s")
|
||||
|
||||
# Brief pause to observe
|
||||
time.sleep(0.3)
|
||||
|
||||
print("\n✓ Test complete! Close viewer to exit")
|
||||
# Verify your kinematics
|
||||
error = np.max(np.abs(joint_targets - actual_positions))
|
||||
print(f"Kinematic verification error: {error:.6f} rad")
|
||||
|
||||
# Keep running
|
||||
try:
|
||||
while robot.viewer and robot.viewer.is_running():
|
||||
time.sleep(0.1)
|
||||
@ -314,5 +344,6 @@ def back_and_forth_test():
|
||||
|
||||
|
||||
if __name__ == "__main__":
|
||||
# Run the back and forth test with smooth convergence
|
||||
back_and_forth_test()
|
||||
demo_position_control()
|
||||
# Uncomment to test with your kinematic code:
|
||||
# example_for_kinematic_code()
|
||||
Reference in New Issue
Block a user