24 accepted papers
Legged robots offer several advantages when navigating unstructured environments, but they often fall short of the efficiency achieved by wheeled robots. One promising strategy to improve their energy economy is to leverage their natural (unactuated) dynamics using elastic elements. This work explor
Fluid-driven soft robots promise high-dimensional motion and cost-effective scalability, but their performance is constrained by the limited flow capacity of compact solenoid valves and the integration challenges of large membrane valves. This paper introduces a modular hybrid valve architecture tha…
In biomechanics and robotics, elasticity plays a crucial role in enhancing locomotion efficiency and stability. Traditional approaches in legged robots often employ series elastic actuators (SEA) with discrete rigid components, which, while effective, add weight and complexity. This paper presents a
For a class of biped robots with impulsive dynamics and a non-empty set of passive gaits (unactuated, periodic motions of the biped model), we present a method for computing continuous families of locally optimal gaits with respect to a class of commonly used energetic cost functions (e.g., the inte…
This paper presents a novel robotic leg design and an associated control approach, which aims at providing an extension to the classical series elastic actuation concept. We propose to directly integrate the series compliance into the structure of the robotic leg itself, as opposed to co-locating sp…
This work introduces a new design paradigm for robotic legs. Our concept extends upon classical series elastic actuation and directly integrates the series compliance into the structure of the leg. This integration reduces the mechanical design complexity and can potentially reduce the overall weigh…
Upright locomotion has many health benefits for patients with spinal cord injury. Passive gait orthoses, such as an isocentric reciprocal gait orthosis (IRGO), allow patients to walk by pushing themselves forward with forearm supports. To move the legs, the IRGO physically couples the motion of stan…
In this work, we present a nonlinear dynamics perspective on generating and connecting gaits for energetically conservative models of legged systems. In particular, we show that the set of conservative gaits constitutes a connected space of locally defined 1D submanifolds in the gait space. These ma
We present a homotopic approach to generating energetically optimal gaits for legged robots that maps passive (i.e., unactuated) gaits of an energetically conservative model of the robot to a model with user-defined target dynamics with dissipation and actuation (i.e., the more “realistic” legged mo…
Controlling soft continuum manipulator arms is difficult due to their infinite degrees of freedom, nonlinear material properties, and large deflections under loading. This letter presents a data-driven approach to identifying soft manipulator models that enables consistent control under variable loa
In this paper, we investigated how the stiffness and damping properties of soft robotic feet affect the stability and energetic economy of bipedal robotic walking. To this end, we manufactured four different spherical feet from the following materials: hollow rubber, Sorbothane, Norsorex, and Neopre…
Controlling soft robots with precision is a challenge due in large part to the difficulty of constructing models that are amenable to model-based control design techniques. Koopman operator theory offers a way to construct explicit linear dynamical models of soft robots and to control them using est…
Soft robots are challenging to model due in large part to the nonlinear properties of soft materials. Fortunately, this softness makes it possible to safely observe their behavior under random control inputs, making them amenable to large-scale data collection and system identification. This paper i…
Safety guarantees are valuable in the control of walking robots, as falling can be both dangerous and costly. Unfortunately, set-based tools for generating safety guarantees (such as sums-of-squares optimization) are typically restricted to simplified, low-dimensional models of walking robots. For m
The compliant structure of soft robotic systems enables a variety of novel capabilities in comparison to traditional rigid-bodied robots. A subclass of soft fluid-driven actuators known as fiber-reinforced elastomeric enclosures (FREEs) is particularly well suited as actuators for these types of sys
In this letter, we identify passive dynamic bounding gaits of quadrupedal robots and investigate the dynamic similarities between these gaits and those of a bipedal model. For this purpose, we develop a passive dynamic bounding model of a quadruped with an extended main body. This model is based on
This paper introduces RAMone, a series-elastic planar biped with knees, built to study the energetics of bipedal locomotion. RAMone is designed to achieve versatile, economical motion using lightweight legs with highly compliant joints. To demonstrate the hardware, we present a virtual-model control…
Should a legged robot use different gaits at different desired speeds? If so, what constitutes these gaits? This work examines these questions through a case study on the planar bipedal robot RAMone. Using a realistic model of the robot, this paper presents the outcome of a series of trajectory opti
Physiological measures, such as pain, anxiety, effort, or energy consumption, play a crucial role in the evaluation and development of assistive robotic devices. Physiological data are collected and analyzed by researchers and clinicians, and are often used to inform an iterative tuning process of a…
This paper uses optimal control to simultaneously optimize the motion and morphology of a realistic model of a 2D Monoped. In particular, we compare the energetics of four different actuator configurations: a parallel elastic actuator (PEA) in the hip and a series elastic actuator in the leg (SEA),
Bellows-like actuators are popular in soft robotic systems. Sensing the movement of these actuators with traditional sensors is challenging. This work proposes and tests a sensing system based on the changing mutual inductance of wire coils on bellows. A method for modeling the changes in mutual ind…
In this paper we use optimal control on a geared electric DC motor to compare the energetic efficiency of a simulation of conceptual monoped hoppers with either parallel elastic actuation (PEA) or series elastic actuation (SEA). The energy is measured using three cost functions: positive actuator wo…
This paper presents a novel variable transmission system that is based on the concept of digital hydraulics. In the proposed system, sets of rolling-diaphragm cylinders are mounted via different effective lever arms to an input and output joint. A variable subset of these cylinders is connected via…
If the control authority of a running system is insufficient to reach a target state in a single step, i.e. if deadbeat control is not possible, then a stabilizing controller is faced with the decision on how to plan intermediate steps. In this work, we compare the performance of a simple greedy con…