Optimal Task-Invariant Energetic Control for a Knee-Ankle Exoskeleton

Lin, Jianping; Divekar, Nikhil; Lv, Ge; Gregg, Robert D.

doi:10.23919/acc50511.2021.9483212

Cited by 5 publications

(18 citation statements)

References 19 publications

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“…This section briefly reviews interconnection and damping assignment passivity-based control (IDA-PBC) for the human-exoskeleton system in [29]. We present the solution to the matching conditions with contact constraints, define the corresponding control law, and define input-output passivity.…”

Section: Review Of Energy Shaping Control For Exoskeletonsmentioning

confidence: 99%

“…where T ex ∈ R 5×1 denotes the new exogenous input compared to [29]. The skew-symmetric matrix J 2 = −J T 2 ∈ R 5×5 represents the extra shaping DOF provided in the interconnection structure by the IDA-PBC method [29]. This introduces…”

Section: B Control Law Satisfying the Matching Conditionsmentioning

confidence: 99%

“…Our recent work in [29] derived an energy-shaping exoskeleton control strategy based on the Interconnection and Damping Assignment Passivity-based Control (IDA-PBC) method [21], [22], which exploits the interconnection structure of the port-controlled Hamiltonian equations. This method enabled additional velocity-dependent modifications to the dynamics without changing the mass/inertia matrix.…”

Section: Introductionmentioning

confidence: 99%

“…Providing a fraction of the normative joint torque offloads musculature as in [7], [9], but in a time-invariant, state-based manner. Our prior work [29] optimized the basis functions to fit weight-normalized able-bodied joint torques across walking gaits on different ground inclines. However, this approach was not flexible enough to reproduce joint torques for a broader set of activities, including stair climbing and stand-to-sit.…”

Section: Introductionmentioning

confidence: 99%

“…However, this approach was not flexible enough to reproduce joint torques for a broader set of activities, including stair climbing and stand-to-sit. Modifications to the gravitational torques vector in [29] depended only on the actuated coordinates, as a convenient way to prove the existence of a closed-loop potential energy and thus passivity and stability. Without additional feedback like the leg's orientation or ground reaction forces (GRFs), the controller was limited to nonlinear spring-like behavior.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Optimally Biomimetic Passivity-Based Control of a Lower-Limb Exoskeleton Over the Primary Activities of Daily Life

Lin

Divekar

Thomas

et al. 2022

IEEE Open J. Control. Syst.

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Task-specific, trajectory-based control methods commonly used in exoskeletons may be appropriate for individuals with paraplegia, but they overly constrain the volitional motion of individuals with remnant voluntary ability (representing a far larger population). Human-exoskeleton systems can be represented in the form of the Euler-Lagrange equations or, equivalently, the port-controlled Hamiltonian equations to design control laws that provide task-invariant assistance across a continuum of activities/environments by altering energetic properties of the human body. We previously introduced a port-controlled Hamiltonian framework that parameterizes the control law through basis functions related to gravitational and gyroscopic terms, which are optimized to fit normalized able-bodied joint torques across multiple walking gaits on different ground inclines. However, this approach did not have the flexibility to reproduce joint torques for a broader set of activities, including stair climbing and stand-to-sit, due to strict assumptions related to input-output passivity, which ensures the human remains in control of energy growth in the closed-loop dynamics. To provide biomimetic assistance across all primary activities of daily life, this paper generalizes this energy shaping framework by incorporating vertical ground reaction forces and global planar orientation into the basis set, while preserving passivity between the human joint torques and human joint velocities. We present an experimental implementation on a powered knee-ankle exoskeleton used by three able-bodied human subjects during walking on various inclines, ramp ascent/descent, and stand-to-sit, demonstrating the versatility of this control approach and its effect on muscular effort.

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Section: Review Of Energy Shaping Control For Exoskeletonsmentioning

confidence: 99%

Section: B Control Law Satisfying the Matching Conditionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Optimally Biomimetic Passivity-Based Control of a Lower-Limb Exoskeleton Over the Primary Activities of Daily Life

Lin

Divekar

Thomas

et al. 2022

IEEE Open J. Control. Syst.

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Modeling, analysis and control of robot–object nonsmooth underactuated Lagrangian systems: A tutorial overview and perspectives

Brogliato

2023

Annual Reviews in Control

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Exoskeletal solutions to enable mobility with a lower leg fracture in austere environments

Johnson

Young²,

Goldman³

et al. 2023

Wearable Technol.

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The treatment and evacuation of people with lower limb fractures in austere environments presents unique challenges that assistive exoskeletal devices could address. In these dangerous situations, independent mobility for the injured can preserve their vital capabilities so that they can safely evacuate and minimize the need for additional personnel to help. This expert view article discusses how different exoskeleton archetypes could provide independent mobility while satisfying the requisite needs for portability, maintainability, durability, and adaptability to be available and useful within austere environments. The authors also discuss areas of development that would enable exoskeletons to operate more effectively in these scenarios as well as preserve the health of the injured limb so that definitive treatment after evacuation will produce better outcomes.

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Optimal Task-Invariant Energetic Control for a Knee-Ankle Exoskeleton

Cited by 5 publications

References 19 publications

Optimally Biomimetic Passivity-Based Control of a Lower-Limb Exoskeleton Over the Primary Activities of Daily Life

Optimally Biomimetic Passivity-Based Control of a Lower-Limb Exoskeleton Over the Primary Activities of Daily Life

Modeling, analysis and control of robot–object nonsmooth underactuated Lagrangian systems: A tutorial overview and perspectives

Exoskeletal solutions to enable mobility with a lower leg fracture in austere environments

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