Evaluation of Physical Interaction during Walker-Assisted Gait with the AGoRA Walker: Strategies Based on Virtual Mechanical Stiffness

Abstract

Smart walkers are commonly used as potential gait assistance devices, to provide physical and cognitive assistance within rehabilitation and clinical scenarios. To understand such rehabilitation processes, several biomechanical studies have been conducted to assess human gait with passive and active walkers. Several sessions were conducted with 11 healthy volunteers to assess three interaction strategies based on passive, low and high mechanical stiffness values on the AGoRA Smart Walker. The trials were carried out in a motion analysis laboratory. Kinematic data were also collected from the smart walker sensory interface. The interaction force between users and the device was recorded. The force required under passive and low stiffness modes was 56.66% and 67.48% smaller than the high stiffness mode, respectively. An increase of 17.03% for the hip range of motion, as well as the highest trunk’s inclination, were obtained under the resistive mode, suggesting a compensating motion to exert a higher impulse force on the device. Kinematic and physical interaction data suggested that the high stiffness mode significantly affected the users’ gait pattern. Results suggested that users compensated their kinematics, tilting their trunk and lower limbs to exert higher impulse forces on the device.

Assessment of a Robotic Walker in Older Adults With Parkinson's Disease in Daily Living Activities

“…As presented in (Sierra et al, 2019 ) between the SW force sensors and the user's handlebar points, there is a vertical misalignment (refer to Figure 1 ). Supported by previous studies (Sierra et al, 2019 , 2021 ), this implies that the resulting forces along the y-axis and z-axis read by the sensors will combine the forces along the y-axis and z-axis at the support points. However, it is possible to estimate that the forces along the y-axis provide essential information related to the user's motion intention.…”

“…Admittance controllers, widely used in SWs, are dynamic models that allow the robotic device to respond efficiently to the user's motion intentions (Jiménez et al, 2019 ). This sort of strategy allows to virtually modify the mechanical impedance of the walker, allowing to emulate different levels of assistance (Jiménez et al, 2019 ; Sierra et al, 2021 , 2022b ). With these controllers, it is possible to generate speed commands according to the user's exerted force and torque.…”

“…With these controllers, it is possible to generate speed commands according to the user's exerted force and torque. Depending on the controller's constants, the SW can resemble lightweight device or a heavy device (Sierra et al, 2021 ). Thus, the purpose of these strategies is to provide users with feelings of easiness and naturalness during physical interaction with the robotic walker.…”

“…It was necessary to adjust the values of the controller parameters to achieve an appropriate SW behavior. For this purpose, the virtual mass ( m ), inertia ( J ), and damping constants ( b l and b a ) were adjusted after several experimental tests with healthy subjects (Sierra et al, 2021 ). In particular, the following values were used: m = 0.5 kg , b l = 4 N .…”

“…Smart Walkers are a potential tool for gait training and assistance due to their simple mechanical structures and multiple interaction interfaces (Scheidegger et al, 2019 ; Aristizabal-Aristizabal et al, 2022 ; Cifuentes and Múnera, 2022 ). The main functionalities of these devices include autonomous navigation systems (Papageorgiou et al, 2016 ), safety and obstacle avoidance modules (Sierra et al, 2018 ), biomechanical monitoring (Caetano et al, 2016 ; Alves et al, 2017 ; Sierra et al, 2021 ), user intention detection mechanisms (Lacey and Rodriguez-Losada, 2008 ), path-following modules (Sierra et al, 2022b ), and people detection systems (Sierra et al, 2019 ). Also, these strategies provide a natural and safe interaction with the user in dynamic and complex environments (Neto et al, 2015 ).…”