###### Abstract  
Intelligent transfemoral prostheses, which have recently been studied, are equipped with a microcontroller, providing appropriate motion functions for their walking environments. Thus, studies have been conducted to estimate user intentions in locomotion movements by applying biomechanical sensors inside the socket. Among them, a pressure sensor is used to determine the intentions of locomotion movements through changes in the internal pressure of the prosthetic socket. However, existing studies have a problem in that the reproducibility of pressure change data is degraded due to the non-detection and saturation of the pressure measurement value. Accordingly, this study proposes a fabrication method for a wide and flexible pressure sensor that can solve this problem and a method for the identification of user intentions in locomotion movements using it. The proposed system was fabricated with Velostat film, which has a smaller noise impact and can be fabricated in various sizes and shapes. The fabricated sensor was attached to four points inside the socket, confirming the possibility of detecting the intention of six movements according to the multi-critical detection method. The proposed pressure-sensor-based intention detection system can be applied individually by prosthetic users through simple tasks. Moreover, it will be universally applicable for commercialization. prostihetic leg; sockets; Velostat; switching locomotion mode; pressure sensor; direction of movement +
Footnote †: journal: Applied Sciences  
15 November 2023  
1 Advanced Prosthesis R&D Team, Korea Orthopedics & Rehabilitation Engineering Center, 10 Beon-gil, Gyeongin-ro, Buryong-gu, Incheon 21417, Republic of Korea; [EMAIL_ADDRESS]  
The transfemoral prosthesis is a device that assists in locomotion and daily life activities among femoral amputees [1, 2]. Early transfemoral prostheses began in the form of no power source and later developed into a way of providing a power source to assist the user's locomotion [3, 4, 5, 6, 7, 8, 9, 10, 11]. The transfemoral prostheses using a power source have been developed to be equipped with a microcontroller for determining various locomotion movements under a finite control state and provide appropriate motion functions for locomotion environments [12, 13]. Accordingly, studies have been conducted together on methods for changing the way of the movement of prosthetic legs in response to changes in user intentions or locomotion environments [14, 15, 16, 17]. Early studies used a method of predefined postures unrelated to the target movement to use changes in hip and knee joint angles as a trigger form or tapping the prosthetic leg in the form of a switch [18]. However, since this method causes unnaturalness unrelated to the target locomotion movement, a technique that makes a relatively natural change was required [19]. In response to this demand, studies have been conducted to monitor the user's locomotion movement by detecting pressure changes inside the socket or EMG signals. Among them, the EMG signal acquisition method can implement a reliable algorithm within limited experimental conditions for a short time. However, the generalization of this method is not easy due to the problem of accumulating muscle fatigue [20; 21]. The pressure change acquisition method is a principle of measuring the physical force acting on the outer wall of the socket according to the movement of the lower limb, and is relatively free from errors caused by the accumulation of muscle fatigue. Therefore, it is possible to compensate for the shortcomings of the EMG sensor for the purpose of detecting the user intention due to discontinuous pressure changes [22; 23]. Based on these characteristics, studies have been conducted to detect pressure changes inside the prosthetic socket to determine the prosthetic user's intention of changing the control method or monitoring locomotion movements [24].