Wear simulation aims to assess wear rates and their dependence on factors like load, kinematics, temperature, and implant orientation. Despite its significance, there is a notable gap in research concerning advancements in simulator control systems and the testing of clinically relevant waveforms. This study addresses this gap by focusing on enhancing the conventional proportional-integral-derivative (PID) controller used in joint simulators through the development of a fuzzy logic-based controller. Leveraging a single-input multiple-output (SIMO) fuzzy logic control system, this study aimed to improve displacement control, augmenting the traditional proportional-integral (PI) tuning approach. The implementation and evaluation of a novel Fuzzy-PI control algorithm were conducted on the Leeds spine wear simulator. This study also included the testing of dailyliving (DL) profiles, particularly from the hip joint, to broaden the scope of simulation scenarios. While both the conventional PI controller and the Fuzzy-PI controller met ISO tolerance criteria for the spine flexion-extension (FE) profile at 1 Hz, the Fuzzy-PI controller demonstrated superior performance at higher frequencies and with DL profiles due to its real-time adaptive tuning capability. The Fuzzy-PI controller represents a significant advancement in joint wear simulation, offering improved control functionalities and more accurate emulation of real-world physiological dynamics.

Background This research presents a novel approach to improve the control performance of joint wear simulators that are used for testing prostheses. For this application, precise controller tuning and minimal tracking errors are essential to meet compliance standards like ISO 18192-1 or ISO 14242-3, and to test under realistic activities of daily living (ADL) scenarios. Methods To address these challenges, the authors propose employing a single-input-multiple-output (SIMO) fuzzy logic control system to augment the traditional proportional-integral (PI) tuning process for joint simulation. To facilitate the development and testing of potential controllers, we utilize a benchtop hardware-in-the-loop (HiL) simulation environment, which facilitated cost-effective rapid control prototyping (RCP). This HiL simulation mimicked joint motion and loading conditions akin to real spinal and hip wear simulators. The objectives of the study are to develop a robust controller for tribological applications and joint simulators and investigate the use of Fuzzy Logic as a possible enhancement of the control system. The Fuzzy-PI controller combines the conventional PI controller with Fuzzy Logic acting as a supervisor, enhancing overall control performance and robustness. The controller adapts to the system's operating range and performance characteristics through a combination of membership functions and control rules. Results Results indicate that for ISO profiles with a fixed 1Hz frequency, both the traditional PI controller and the Fuzzy-PI controller perform equally well. However, as the frequency of the ISO profile increases or when handling ADL profiles with multiple frequency components, the Fuzzy-PI controller outperforms the PI controller. This was attributed to Fuzzy-PI's real-time adaptive capability to tune PI gains as frequency demands changed through a profile, providing a more robust and superior performance, particularly in challenging scenarios. Conclusions In conclusion, the Fuzzy-PI controller represents a promising advancement for joint wear simulators, offering improved control capabilities and better simulation of real-world physiological conditions.

Hardware-in-the-loop (HIL) simulation is an advanced technique for developing and testing complex real-time control systems. This paper presents the benefits of HIL simulation to develop, test and validate advanced control algorithms used in an artificial joint wear simulator for the tribological testing of prostheses.A benchtop HIL setup is created for experimentation, controller verification, and validation purposes, allowing different control strategies to be tested rapidly in a safe environment. The HIL simulation attempts to replicate similar joint motion and loading conditions of that of the spinal wear simulator. The simulator contains a four-bar link powered by electromechanical actuators. As a result, the implant articulates with an angular motion specified in the international standards, ISO-18192-1, that defines fixed sinusoid motion and load profiles for wear testing of both lumbar and cervical disc implants.Using a PID controller, a velocity-based position control algorithm was developed to interface with the benchtop setup that performs HIL simulation. The simulation results strongly support the efficacy of the test setup using HIL simulation to verify and validate the accuracy and robustness of the prospective controller before its deployment into the spinal wear simulator. This method of testing controllers enables a wide range of possibilities to test advanced control algorithms that can potentially utilize real-world data of patients performing daily living activities that place adverse demands on the artificial joint.

Home-based robotic technologies may offer the possibility of self-directed upper limb exercise after stroke as a means of increasing the intensity of rehabilitation treatment. The current literature has a paucity of robotic devices that have been tested in a home environment. The aim of this research project was to evaluate a robotic device Home-based Computer Assisted Arm Rehabilitation (hCAAR) that can be used independently at home by stroke survivors with upper limb weakness.

Advances in direct mechanical ventricular actuation devices have been limited by the inability to test the whole device interaction in-vitro. In this study, we introduce a novel technique to produce a realistic, multimodality cardiovascular simulator to mimic the activity of a beating heart. To achieve the mechanical representation of the heart, each ventricle was defined by a real-time modifiable semicircular pattern of post-buckled spring steel strips with adjustable boundary attachments. The mechanical properties of these strips such as stiffness, length, width and boundary conditions approximated the local and global biomechanical properties of the native heart. This physical heart model interfaced with a mathematical model of the cardiovascular system based on hardware-in-the-loop simulation. In-vitro experiments were carried out in an attempt to investigate into the effect that the DMVA system has on PV loop, cardiac output, and overall hemodynamics under different physiological conditions. By employing this in-vitro setting, assist devices can be physically applied to the circulatory models and assessed before animal or clinical trials are conducted. This will significantly aid device behavioural understanding, development time and cost during device's prototyping.

A novel compliant actuator based upon the compliance of a buckled thin strip is presented. It is suggested that the actuator can be used for a point contact attachment or to generate a 2-D or 3-D compliant surface. Compliance variation was obtained by changing the distance between the ends of the buckled strip using a linear actuator and by altering the end attachments from hinged to clamped. A mathematical model is developed and experimentally validated to predict the shape of the compliant surface so that its profile can be controlled and matched to a target surface shape. The general characterization of the actuator is presented here in terms of compliance modification and frequency response. Results demonstrated that actuator compliance could be increased 2× by adjustment of the end boundary attachments, and 8× by adjusting the end displacement as well. These increases could be achieved “on-the-fly”, without reconfiguring the system. The actuator also generated a stable, linear response in the design range of up to 4.0 Hz. In conclusion, we have shown that a buckled strip/linear motor combination can produce an accurate, predictable, and controlled active compliance actuator suitable for a range of applications, but designed here for applications involving interaction with or simulation of biological tissues.

Heart disease is the developed world's largest killer. Transplantation of the failing heart remains the most effective treatment currently employed, but demand far exceeds donor supply. In a bid to address this imbalance, the use of mechanical circulatory support has been explored since the mid-1960s. This paper utilizes one such device, which achieves assistance by mechanically compressing the epicardial surface of the failing heart. The circumferential normal loading of the device is investigated, showing how frictional effects inherent to the device's operation affect localized surface pressure. Results showed that as distance from the device's actuator increased, assistive systolic force reduced, whilst device constriction to ventricular filling detrimentally increased. Active device relaxation was shown to limit the diastolic effect outlined above, providing the simulated diseased heart with an improved cardiac output. The results also raise questions concerning device in-vivo positioning and short-comings with the current heart simulator.