Emulation involves converting simulated kinematics and kinetics into real-world physical effects. A common method for achieving this in robotic systems is hardware-in-the-loop simulation, where a system under test is driven by outputs from a virtual model, thereby replicating the dynamics of a non-physical system. This approach has diverse applications across research fields, with notable examples including physical human-robot interaction and spacecraft development testbeds. Using robotic arm systems as conduits for physical emulation, this work presents two approach applications: one focusing on the design of a novel full-body haptic exoskeleton and the other on the control of an Ocean World lander-manipulator testbed for advanced sampling autonomy evaluation.
The full-body haptic system, referred to as the Virtual Reality Exoskeleton (V-Rex), is a novel design incorporating five industrial robotic arms to enable localized end-effector interactions with a human user. Two arms interface with the upper limbs, two with the lower limbs, and one provides active body support for gravity offloading and fall protection. Each arm operates under admittance control, driven by an underlying virtual dynamic model that can also interact with virtual objects in a scene. Experimental verification demonstrates the system's tunability for emulating various virtual models and highlights human interaction with virtual solid objects through haptic force feedback. The system is further validated for tracking and real-time control performance. Across all experiments, the system performs as intended, establishing it as a robust framework for potential robotic rehabilitation tasks.
Ensuring safety in physical human-robot interaction presents significant challenges due to variations in hardware and control architectures across robotic systems, often leading to system-specific, ad-hoc solutions. To address this, we propose a redundant three-tier safety framework designed for industrial robotic arms. This framework ensures safety at the reference-generation level by imposing soft virtual bounds to restrict virtual dynamics, as well as hard bounds, which enforce infinitely stiff constraints. Additionally, we introduce a novel collision avoidance method for serial manipulators and multi-segment entities using partial Jacobians. At the command level, safety is verified through checks that validate motions before they are sent to the hardware, with fault detection and avoidance systems providing secondary redundancy. Physical safety is further addressed through real-time monitoring of robot states and standard hardware safety measures, such as e-stops and quick releases for human operators. Experimental results validate the effectiveness of soft and hard bounds, multi-arm collision avoidance, and the fault management system. In all scenarios, the system confines operations to safe working spaces, demonstrating the efficacy of this safety-focused admittance control framework for industrial robotic arms.
The second system discussed is the Ocean World Lander Autonomy Testbed, developed at NASA's Jet Propulsion Laboratory to evaluate autonomy technologies for potential lander missions to Ocean Worlds. To advance lander autonomy development, a novel control method has been devised to physically emulate the dynamics of a lander-manipulator system on a low-gravity body. Using hardware-in-the-loop simulation, this method enables physical simulant sampling interactions for testing arbitrary spacecraft controllers. Unlike similar systems in the literature, our approach emulates robotic arm joint torques in real-time without requiring external offloading hardware. Physical emulation experiments conducted with the testbed's robotic arm and Stewart platform demonstrate the versatility of this offloading method in replicating the behavior of diverse lander-manipulator systems using a single test setup. The emulated systems span various gravity environments, a lightweight flight-like arm, and modified physical simulant properties. This methodology, integrated with the hardware testbed, provides a novel tool for spacecraft design, supporting tasks such as flight arm motor torque sizing, low-level controller tuning for flight software, and estimating power requirements for sampling tasks.
