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Phantom limb with Variable Stiffness Actuator
(2025) Falke, Robin; Kelemit, Melvin; Lee, Sunkook; Sandevi, Atlas; Lannrup Signäs, Filip
Technology and healthcare are improving faster than ever, and with it comes an increased demand to be able to test new innovations before they get approved for use. However, with strict guidelines on how these tests are allowed to be performed, it is not always that easy. One of the areas affected by these guidelines is the continued development of better exoskeletal arms for people with impaired movement. Due to the risk of potential injury when testing these products in a patient who does not have full control over their arm, and who might experience rapid and spasmodic movement in it, testing on people is highly limited [1].
Therefore, this thesis presents the design and development of a robotic phantom limb with a VSA (Variable Stiffness Actuator), intended as a test platform for exoskeletal devices used in rehabilitation. The motivation comes from the need to test exoskeletons safely without relying on human subjects, particularly for conditions involving involuntary or spasmodic movements. The project combines mechanical, electrical and control system engineering to create an anthropomorphic arm capable of replicating realistic joint dynamics and variable stiffness behaviors.
Key objectives included designing the VSA using nonlinear springs to mimic human muscle behavior, implementing a control system using an STM32 microcontroller and ROS2 architecture, and integrating sensors such as IMUs, hall sensors, and force-torque sensors to monitor system performance. The system was modeled and simulated in Simulink to validate control strategies and mechanical performance prior to physical implementation. The experimental results demonstrated that the prototype could achieve the target stiffness levels, torque outputs, and angular positions necessary to simulate human arm movement under various conditions. This work contributes a valuable tool to the advancement of rehabilitation robotics by enabling more efficient and safer testing of assistive devices, ultimately aiming to accelerate the development and clinical deployment of user-centered robotic systems.
Adaptive Exoskeleton for Knee Injury Rehabilitation
(2025) Backman, Albin; Bukowski, Olle; Gustavsson, Theo; Ivarsson, Erika; Ljungqvist, David; Sare, Olivia
This project presents the continued development of a single-joint exoskeleton intended for knee rehabilitation. The overall goal was to contribute to more effective, individualized rehabilitation by enabling an exoskeleton system that is able to provide transparent, torquebased assistance and track limb motion in real time. Such a system could ultimately reduce recovery time, support at-home therapy and improve the quality of care.
Moving towards this goal, the project focused on introducing sensing and control capabilities. A ROS2-based software architecture was implemented to coordinate real-time communication between hardware components. The actuator was successfully integrated via CAN-bus and operated under open-loop control. However, torque feedback had to be estimated indirectly using current measurements as no dedicated torque sensor was available. The IMU delivered usable quaternion data, but filtering and sensor fusion were not fully completed due to time constraints.
While a fully functional control system was not achieved, the system now provides real-time data flow and basic motion control. The final framework offers a solid technical foundation for future work on further IMU- and actuator-integration, feedback control and clinical applications.
Designing Next-Gen Adaptive Exoskeleton for Physiotherapy and Rehabilitation
(2025) Hansson, Adam; Hedberg, Albin; Klasson, Emil; Lago, Isabella; Lindeberg, Malte; Hjalmarson, Viktor
Robotic knee exoskeletons have emerged as promising tools for enhancing gait training, with the potential to accelerate rehabilitation and aid the therapists throughout the entire process. However, many current solutions are limited by bulky designs, lack of adaptability, and poor real-world usability. This report presents the development of a modular, motorized and instrumented knee exoskeleton prototype designed to be lightweight, user-friendly, and interchangeable between the left and right leg. The design incorporates a quick-release actuator mechanism, integrated force sensors, an IMU and an encoder, laying the groundwork for more accessible and practical assistive devices.
CFD-Based Sensitivity Study of Flow and Design Parameters in Multiphase Flow Meters. Analyzing the Impact of Variable Conditions on Homogeneity and Measurement Accuracy
(2025) Nilsson, Elias; Vassilev, Maria
In subsea oil- and gas applications, multiphase flow meters (MPFM) are used to measure volumetric flow rates of oil, gas and water produced from a well, without first separating the phases. When well productions decline the flow may become unstable, requiring additional controls. In these cases MPFMs are useful instruments to detect well instability, blockages and disturbances so that the well can be controlled and stabilized in real time. Variations in flow regime and homogeneity in the Venturi-based MPFM may affect the accuracy of measured volume flow. Additionally, understanding slip velocity between phases is crucial for formulating an accurate slip model to compute phase volume flow rates.
In this project, the sensitivity of the MPFM to flow- and geometrical parameters is studied by modeling and simulating the MPFM using CFD. This gives insight into how MPFM design and operating conditions influence measurement certainty on a macroscopic scale, while also allowing for the investigation of smaller scale phenomena. Time-averaged mean values and periodic behaviors of the flow parameters are evaluated to give insight into the flow behavior and the MPFM sensitivity to flow and design parameters. The homogeneity and mixing of the flow before entering the MPFMs is evaluated, to understand how operating conditions and geometry changes affect the flow characteristics considering MPFM accuracy. Additionally, a
suitable CFD modeling technique is found to aid in the design and development of future MPFMs. The modeling technique is evaluated in terms of accuracy, quality and computational expense.
In this study, a suitable modeling method was identified using Eulerian Multiphase models. These models have high accuracy and is effectively capturing the flow behavior while being computationally efficient. The slip-ratios evaluated showed that for increased pressure and viscosity the liquid film, dispersed, and overall slip decreased while for design changes the slip had more mixed results. The sensitivity study revealed that the MPFM’s sensitivity to geometrical parameters, such as blind-T depth and vertical entrance length, was minimal. Operating conditions, especially pressure and liquid viscosity, play a major role in shaping the flow regime and phase mixing. These factors can significantly affect MPFM accuracy if they are not properly accounted for in the interpretation models.
Sensor-Based Virtual Fences for Industrial Robot Safety
(2025) Abo Saleh, Nour; Grahn, Johan; Grunewald, Knut; Petersén, Hanna; Segerberg, Filip
In industrial environments, safety has traditionally been ensured using physical barriers such as fences or enclosures to separate humans from robotic systems. While effective, these static solutions limit flexibility and make it difficult to adapt the layout to changing production needs. As factories become more dynamic and collaborative, there is a growing need for smarter, more adaptable safety systems. In this project, a virtual safety system for an industrial robot was developed using LiDAR sensors and real-time data processing. The system was designed to replace traditional physical barriers by creating three safety zones around the robot a safe zone, a warning zone and a restricted zone, depending on the distance of approaching objects. The sensors and control electronics were built and tested in real life, while the behavior and reactions of the robot were evaluated through simulation. The system continuously monitored the area at a height of 15 to 20 cm above the floor and successfully detected objects and classified them into the correct zones. The tests showed that the system detected all intrusions correctly in both warning and stop zones. The average response time was around 10 ms, which is fast enough for real-time feedback. However, the system experienced false intrusions in some cases, especially when using larger zones and more active components—up to 601 false triggers during 20 minutes recorded in one test. The results demonstrate that the system was able to trigger appropriate responses based on risk level, and show that virtual safety zones could be a viable and flexible alternative to traditional physical fences in industrial robot applications.