Project Title

Design and Development of a Robotic Compliant Knee Joint

Academic department under which the project should be listed

SPCEET - Mechanical Engineering

Faculty Sponsor Name

Ayse Tekes

Not Required

Abstract (300 words maximum)

Lower extremity loss or impairment which challenges the mobility of the people is caused by many reasons such as diabetes, stroke, spinal cord injury and ageing. Recently, there has been a huge demand for assistive knee devices which improve the quality of the people who have lower limb disorders.

These devices are commonly called as exoskeletons which are wearable prosthetic robots that couples with human body and augment and restore human performance during motion. Robotic prosthetic based systems are widely used in assistance and rehabilitation of patients with permanent or temporary dysfunctionality providing complete or partial replacement of

related limbs.

Knee joint is the most important part of human lower limb prosthesis which provides healthy locomotion and is responsible to enable smooth control of a stable gait. The knee is a complicated structure consisted of a number of important ligaments, bones tendons and muscles and it is one of the most stressed joints in the body. On the other hand, walking action is a combination of complex set of movements which makes it extremely difficult to model the exact human walking. There have been several prosthetic systems developed to mimic the natural muscle actions that act like the knee joint. Single axis prosthesis provides a one degree of freedom motion that can bend around a fixed center of rotation. Although these early prostheses are easy to implement and relatively cheaper, they do not provide high stability and hence the amputee has to depend on his own muscle control. Single axis prosthesis are commonly used by children and patients who need walking assistance.

Most of the single axis and polycentric based knee prosthesis are passive devices integrating hydraulic or pneumatic controllers allowing the knee to adjust walking speed. On the other hand, there have been recently developed microcontroller based active knee devices utilizing various sensors and motorized mechanisms with complex control algorithms. Although these active devices have better gait stability applying controlled external power and healthy knee behavior with reduced fall risk of the amputee, they are expensive, heavy and need large amount of energy to operate.

In general, currently available knee prosthesis designs include several metal parts such as motors, gears and springs which makes the system extremely bulky not allowing small children to use them comfortably. In addition, since the knee prosthesis had a fixed size and very limited adjusting capability, it is always a challenge for the children who are still in growing stage. Therefore, for pediatric applications, it is desired to have cheap, light-weighted and easily replaceable prosthesis devices which would also provide flexible motion. Compliant mechanisms are good candidates offering many advantages including lighter weight, easy and cheap manufacturing process, monolithic design and reduced friction which makes them potentially suitable for pediatric prosthesis knee systems.

In this study we present the design of a monolithic, compliant and 3D printed knee joint that is low-cost and simple designed to replace the existing bulky and rigid knee joints. The forward motion and snapping to complete a successful walking gait are achieved by the large deflection of flexure hinges. Knee joint performance is tested on a robotic knee.

Project Type

Oral Presentation (15-min time slots)

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Design and Development of a Robotic Compliant Knee Joint

Lower extremity loss or impairment which challenges the mobility of the people is caused by many reasons such as diabetes, stroke, spinal cord injury and ageing. Recently, there has been a huge demand for assistive knee devices which improve the quality of the people who have lower limb disorders.

These devices are commonly called as exoskeletons which are wearable prosthetic robots that couples with human body and augment and restore human performance during motion. Robotic prosthetic based systems are widely used in assistance and rehabilitation of patients with permanent or temporary dysfunctionality providing complete or partial replacement of

related limbs.

Knee joint is the most important part of human lower limb prosthesis which provides healthy locomotion and is responsible to enable smooth control of a stable gait. The knee is a complicated structure consisted of a number of important ligaments, bones tendons and muscles and it is one of the most stressed joints in the body. On the other hand, walking action is a combination of complex set of movements which makes it extremely difficult to model the exact human walking. There have been several prosthetic systems developed to mimic the natural muscle actions that act like the knee joint. Single axis prosthesis provides a one degree of freedom motion that can bend around a fixed center of rotation. Although these early prostheses are easy to implement and relatively cheaper, they do not provide high stability and hence the amputee has to depend on his own muscle control. Single axis prosthesis are commonly used by children and patients who need walking assistance.

Most of the single axis and polycentric based knee prosthesis are passive devices integrating hydraulic or pneumatic controllers allowing the knee to adjust walking speed. On the other hand, there have been recently developed microcontroller based active knee devices utilizing various sensors and motorized mechanisms with complex control algorithms. Although these active devices have better gait stability applying controlled external power and healthy knee behavior with reduced fall risk of the amputee, they are expensive, heavy and need large amount of energy to operate.

In general, currently available knee prosthesis designs include several metal parts such as motors, gears and springs which makes the system extremely bulky not allowing small children to use them comfortably. In addition, since the knee prosthesis had a fixed size and very limited adjusting capability, it is always a challenge for the children who are still in growing stage. Therefore, for pediatric applications, it is desired to have cheap, light-weighted and easily replaceable prosthesis devices which would also provide flexible motion. Compliant mechanisms are good candidates offering many advantages including lighter weight, easy and cheap manufacturing process, monolithic design and reduced friction which makes them potentially suitable for pediatric prosthesis knee systems.

In this study we present the design of a monolithic, compliant and 3D printed knee joint that is low-cost and simple designed to replace the existing bulky and rigid knee joints. The forward motion and snapping to complete a successful walking gait are achieved by the large deflection of flexure hinges. Knee joint performance is tested on a robotic knee.