Advanced Robotic Manipulators Lab
Treadmill with Adjustable Stiffness (TwAS)
Surface stiffness plays an important role in human locomotion mechanics. This would affect both the energy expenditure and gait of the human. These effects have been numerically investigated for runners. Such effects, however, have not been fundamentally addressed for other locomotion scenarios such as walking or running. Towards this goal, we designed and developed a novel Treadmill with Adjustable Stiffness (TwAS) with the Ability to Regulate the Vertical Stiffness of the Ground. The novelty of the system is on its stiffness adjustment mechanism which allows the “vertical” stiffness of the surface to change quickly (less than 0.5 second) from completely passive (i.e. theoretically zero stiffness) to extremely rigid (i.e. theoretically infinite stiffness) with minimum energy consumption, independent of the location of the person over the treadmill. The design also allows for bilateral surface stiffness regulation (i.e. both legs, independently) that is an extremely helpful criterium in studying the locomotion mechanics and eventually gaining valuable insights into best rehabilitation strategies of mobility impaired patients. In order to show the proof of concept, we are conducting experiments to show the effect of surface stiffness regulation on the metabolic cost and gait of a healthy subject.
Remotely Actuated Lower Extremity Exoskeleton
Most of these exoskeletons are actuated by geared electromagnetic actuators. Actuators are located at each joint of these exoskeletons in alignment with center of rotation of the corresponding human joints. However, available space at each joint to locate the actuator is limited especially at the ankle join. Furthermore, this traditional way of locating the actuators at the joints limits maneuverability of the wearer. The research thrust of this proposal is the development of a lower body exoskeleton for able-bodied operators. The goal is to improve physical capability of soldiers in different load tasks while maintaining user safety and maneuverability while reducing muscular and metabolic fatigue during load carriage activities.
Electromagnetic Soft Actuators (ESAs)
Current wearable rehabilitation and assistive devices are either 1: powerful and active but bulky and made of rigid elements such as exoskeletons and prosthesis, or 2: flexible and passive but have limited functionalities, such as joint braces. Realizing a wearable rehabilitation technology that is light and soft yet active and powerful has been a grand challenge for researchers due to a persisting gap in current actuation technology: there is still no soft actuator that is portable, i.e. can be operated by on-board power sources, scalable to be adopted to different joint sizes and still can have short response time and high output force-to-size ratio in order to be able to assist joint's motions. It is believed that the emerging field of soft robotic will be the foundation of future assistive technology, if the above-mentioned gap in regards to the actuator part can be filled. Without meeting this need, rehabilitation and assistive technologies will be limited to current passive braces or bulky exoskeletons and prosthetic devices that are proven to not be very efficient and functional for many applications and are sometimes even dangerous for patients.
Motivated by the aforesaid challenges, a novel Electromagnetic Soft Actuator (ESA) is presented which is highly scalable and can be easily actuated by on-board batteries. ESAs are capable of mimicking behavior of Actin and Myosin filaments by producing linear force and contraction. The ESA is highly scalable which allows us to miniaturize it and create artificial sarcomere by assembling them in parallel and series fashion.
Quasi-Passive Shoulder Exoskeleton
Human walking gait is touted to be the most efficient biped walking gait. With necessity and purpose determining the varied types of gait that we follow during locomotion, one major factor that controls or differentiates human gaits is Arm Swing. Earlier studies proved that there is 7% reduction in the metabolic cost due to the arm swing. However, when army soldiers carry their weapon from one place to another, people who look for rehabilitation of their normal gait after an accident and arm amputees consume more energy during walking. The primary goal of the project is to determine which type of gait caused by arm swing requires high metabolic cost and the secondary goal was to look out for ways to reduce the metabolic cost by providing alternate ways for the arm swing if it is required.
A group of 6 subjects was asked to walk in four different gaits on a treadmill to record and analyze their oxygen levels. The goal was to enable subjects to walk with a custom designed upper body exoskeleton. Accordingly, a quasi-passive exoskeleton which suits all human bodies was designed and 3D printed to perform experiments to test the reduction of metabolic cost in folded arm walking gait. The empirical results from the tests validate a 10% reduction in the metabolic cost of walking aided by the use of the exoskeleton designed.
