Kangaroo

Kangaroo, developed by PAL Robotics, is a highly dynamic bipedal humanoid robot platform primarily engineered for advanced research in legged locomotion, biomechanics, and dynamic motion control. Evolving from an initial prototype showcased around 2022-2023 to a commercially available product by August 2024, Kangaroo represents a significant milestone in PAL Robotics' portfolio of research robots. Its architecture features a novel leg design utilizing custom high-performance linear ball screw actuators with integrated force sensors, arranged in closed kinematic chains. This configuration allows for proximal actuation—placing motors close to the hip joint—minimizing moving inertia, enhancing efficiency, and enabling agile maneuvers such as running, jumping, squatting under load, and impact recovery. Each leg provides 6 degrees of freedom (DoF): hip yaw, hip roll, hip pitch, leg length extension, ankle pitch, and ankle roll, with torque ranges up to 230 Nm at hip pitch and linear speeds up to 3 m/s for leg extension. The total actuated DoF reaches 28 in full configurations, including 12 for legs, 14 for dual 7-DoF arms (shoulder yaw/pitch/roll, elbow, wrist roll/pitch/yaw), and 2 for torso (pitch/yaw). The robot's control architecture leverages ROS 2 for modularity, with a high-frequency EtherCAT loop at 2 kHz (1 kHz in Lite version) for real-time performance. Key controllers include Whole Body Inverse Dynamics (WBID) for balancing and multi-contact scenarios, Zero Moment Point (ZMP)-based position control approximating a Linear Inverted Pendulum Model (LIPM) stabilized via Linear Quadratic Regulator (LQR), and closed-loop force/torque control at the joint level. Software supports non-linear transmissions and virtual constraints for handling closed chains. Decentralized electronics with individual actuator boards reduce cabling by 40%, improving robustness. Onboard computing comprises dual Intel i7 PCs (32GB RAM, 1TB SSD)—one for control, one for multimedia/perception—plus optional NVIDIA Jetson Orin AGX/NX for AI workloads like neural networks and reinforcement learning (RL), though no proprietary AI models are integrated; users can implement custom RL policies for locomotion via simulators like Isaac Lab, MuJoCo, or Gazebo. Perception in advanced versions includes 4x Intel RealSense D435i RGB-D cameras for navigation and footstep planning. Materials blend lightweight carbon-fiber tubes for structural elements with flexible/rigid composites for impact absorption, yielding weights from 35-56 kg across Lite, Standard, and Plus variants. Autonomy reaches 4 hours per charge via efficient power boards. Safety features encompass wireless e-stop, protective waist shielding, and force-limited interactions. Real-world deployments include the PRIMI EU project (2023-2027), where an upgraded Kangaroo integrates event-driven dynamical systems for cognitive control and neuromorphic rehabilitation robotics, and the first commercial unit delivered to TU Wien in 2024 for PhD-level locomotion research. Additional applications span healthcare rehab, industrial precision tasks, and academic AI-robotics experiments, with demos showing free-walking, heavy squats, and stable balancing. Kangaroo's energy-efficient design and custom actuators position it as a benchmark for next-gen bipedal platforms, fostering breakthroughs in torque-controlled locomotion amid unknown terrains.