Periodic Reporting for period 1 - SoftHand Pro-H (A Soft Synergy-based Hand Prosthesis with Hybrid Control)
Reporting period: 2017-01-01 to 2018-03-31
Summary of the context and overall objectives of the project
The SoftHand Pro-H Proof of Concept grant was ideated by the Istituto Italiano di Tecnologia (IIT) and qbrobotics and borne out of the results of the SoftHands European Research Council Advanced Grant. In SoftHands, we have achieved not only a more thorough understanding of the organization and control of human hands, but also a principled approach to taming the complexity of hand design. One of the results of the SoftHands project was a novel, underactuated, flexible yet robust hand prosthesis based on human hand synergies. (Synergies are a neuroscientific theory explaining how the brain organizes and manages complex movements, such as the coordination of the joints in the human hand.)
The aim of the SoftHand Pro-H Proof of Concept project was to study the feasibility of applying the SoftHand technology to create work-oriented prostheses, by experimenting with a novel hybrid approach between electric and body-powered prostheses. Electric prostheses (EP) are usually controlled by muscle signals in the residual limb and often have an anthropomorphic shape. Body-powered prostheses (BP) are typically controlled by shoulder movements on the un-affected side and often have a more functional or task oriented shape (classically a split hook). Each type of prosthesis has distinct advantages and disadvantages, thus neither can be declared inherently “better” than the other. BPs are lighter-weight and robust but require wearing a shoulder harness that can be bulky and cause discomfort over time, particularly in high-force situations. EPs tend to provide a more aesthetically-pleasing, especially in social situations, and physically comfortable solution but are more costly and heavy.
BPs tend to be especially favored in manual work situations, such as farming or factory work, for their robustness and precision. Further, the shoulder harness connects directly to the prosthesis, pulling it either open or closed in response to shoulder movement, thus providing the user with inherent feedback about the prosthesis’ aperture. In this project, we focused on this work application, aiming to provide the flexibility, anthropomorphism, and strength of the SoftHand Pro with the ease of use and natural feedback of the shoulder harness. Additionally, we aimed to explore making the prosthesis more robust to harsh environments (water, dirt, etc) and lighter by distancing certain key components of the prosthesis from the hand itself. We considered three key components and three possible placements: the electronics, motor, and battery could be placed on the hand, in the socket (the interface between the hand and the residual limb), or on the body of the user.
Considering all possible combinations, 27 potential solutions were derived, which were then narrowed down to 8 by applying various criteria. These criteria, without going into extensive detail, were selected to manage prosthesis weight and shape and avoid wasted space. Four of these were then selected to develop to a prototype level within this project, for simplicity called Configurations A, B, C, and D. Configuration A and B both house the motor on the back of the hand, much like the original SoftHand Pro, but place the electronics and battery either in the socket or on the body, respectively. Configuration C displaces all three components into a single unit that can be worn on the body, thus rendering it the most lightweight at the residual limb. Finally, Configuration D maintains both the motor and electronics on the hand, while the battery is worn on the body.
In order to test the four prototypes, we performed what is known as a crossover study in two phases, the first phase with limb-intact participants and the second with participants with limb loss. (A crossover study is when a single participant tries multiple types of interventions or, in our case, devices to enable direct comparison.) In phase one, ten participants tested all four prostheses. They trained with study staff on a particular configuration until they could confidently and reliably succeed at two simple tasks: building a pyramid with plastic cups and folding a t-shirt. They were then rated on their functional ability with the prosthesis using two clinical tests. The first asks the user to complete a standardized activity, like setting a table, while rating their ability to use and control the prosthesis. The second asks the user to pick up small blocks from a compartment and move them over a barrier into another compartment. This "pick-and-place" task tests both dexterity and speed. Finally, the participant completed the "system usability scale," a questionnaire often employed to understand the ease of use and satisfaction with new technology. This process was repeated for the other three prototypes and an additional questionnaire was completed at the end to compare them. Each participant tested the prostheses in a random order.
From these tests, Configurations A and B nearly tied, both ranking the highest in the objective, clinical tests, while A was rated considerably higher than B in the subjective questionnaires. We then proceeded to test two configurations with three participants with limb loss. We selected Configuration A, since it was the highest performer and most well-liked, and Configuration C to test. Configuration B is nearly identical to A, save for the battery placement. Configuration C was the third-highest performer overall and was substantially different than the A and B Configurations. In testing with participants with limb loss, Configuration A scored higher on all four tests for two participants; the third participant’s results were mixed, with A scoring higher than C on one objective and one subjective test and C scoring higher than A on the other of each test.
Both sets of testing show the promise primarily of Configuration A. Qualitative (participant comments) and quantitative (test scores) results are being used to improve this configuration. The results are also being shared with a concurrent EU-funded project, SoftPro. SoftPro is a four-year, multi-national collaborative project with aims across rehabilitation and prosthetics. The SoftHand Pro is being further developed in this project, and IIT and qbrobotics are both involved in the project, making it the natural next to further the results of this project.
The aim of the SoftHand Pro-H Proof of Concept project was to study the feasibility of applying the SoftHand technology to create work-oriented prostheses, by experimenting with a novel hybrid approach between electric and body-powered prostheses. Electric prostheses (EP) are usually controlled by muscle signals in the residual limb and often have an anthropomorphic shape. Body-powered prostheses (BP) are typically controlled by shoulder movements on the un-affected side and often have a more functional or task oriented shape (classically a split hook). Each type of prosthesis has distinct advantages and disadvantages, thus neither can be declared inherently “better” than the other. BPs are lighter-weight and robust but require wearing a shoulder harness that can be bulky and cause discomfort over time, particularly in high-force situations. EPs tend to provide a more aesthetically-pleasing, especially in social situations, and physically comfortable solution but are more costly and heavy.
BPs tend to be especially favored in manual work situations, such as farming or factory work, for their robustness and precision. Further, the shoulder harness connects directly to the prosthesis, pulling it either open or closed in response to shoulder movement, thus providing the user with inherent feedback about the prosthesis’ aperture. In this project, we focused on this work application, aiming to provide the flexibility, anthropomorphism, and strength of the SoftHand Pro with the ease of use and natural feedback of the shoulder harness. Additionally, we aimed to explore making the prosthesis more robust to harsh environments (water, dirt, etc) and lighter by distancing certain key components of the prosthesis from the hand itself. We considered three key components and three possible placements: the electronics, motor, and battery could be placed on the hand, in the socket (the interface between the hand and the residual limb), or on the body of the user.
Considering all possible combinations, 27 potential solutions were derived, which were then narrowed down to 8 by applying various criteria. These criteria, without going into extensive detail, were selected to manage prosthesis weight and shape and avoid wasted space. Four of these were then selected to develop to a prototype level within this project, for simplicity called Configurations A, B, C, and D. Configuration A and B both house the motor on the back of the hand, much like the original SoftHand Pro, but place the electronics and battery either in the socket or on the body, respectively. Configuration C displaces all three components into a single unit that can be worn on the body, thus rendering it the most lightweight at the residual limb. Finally, Configuration D maintains both the motor and electronics on the hand, while the battery is worn on the body.
In order to test the four prototypes, we performed what is known as a crossover study in two phases, the first phase with limb-intact participants and the second with participants with limb loss. (A crossover study is when a single participant tries multiple types of interventions or, in our case, devices to enable direct comparison.) In phase one, ten participants tested all four prostheses. They trained with study staff on a particular configuration until they could confidently and reliably succeed at two simple tasks: building a pyramid with plastic cups and folding a t-shirt. They were then rated on their functional ability with the prosthesis using two clinical tests. The first asks the user to complete a standardized activity, like setting a table, while rating their ability to use and control the prosthesis. The second asks the user to pick up small blocks from a compartment and move them over a barrier into another compartment. This "pick-and-place" task tests both dexterity and speed. Finally, the participant completed the "system usability scale," a questionnaire often employed to understand the ease of use and satisfaction with new technology. This process was repeated for the other three prototypes and an additional questionnaire was completed at the end to compare them. Each participant tested the prostheses in a random order.
From these tests, Configurations A and B nearly tied, both ranking the highest in the objective, clinical tests, while A was rated considerably higher than B in the subjective questionnaires. We then proceeded to test two configurations with three participants with limb loss. We selected Configuration A, since it was the highest performer and most well-liked, and Configuration C to test. Configuration B is nearly identical to A, save for the battery placement. Configuration C was the third-highest performer overall and was substantially different than the A and B Configurations. In testing with participants with limb loss, Configuration A scored higher on all four tests for two participants; the third participant’s results were mixed, with A scoring higher than C on one objective and one subjective test and C scoring higher than A on the other of each test.
Both sets of testing show the promise primarily of Configuration A. Qualitative (participant comments) and quantitative (test scores) results are being used to improve this configuration. The results are also being shared with a concurrent EU-funded project, SoftPro. SoftPro is a four-year, multi-national collaborative project with aims across rehabilitation and prosthetics. The SoftHand Pro is being further developed in this project, and IIT and qbrobotics are both involved in the project, making it the natural next to further the results of this project.