286 research outputs found

    Towards IMU-based Full-body Motion Estimation of Rough Terrain Mobile Manipulators

    Get PDF
    For navigation or pose estimation, strap-down Micro-Electro-Mechanical System (MEMS) Inertial Measurement Units (IMU) are widely used in all types of mobile devices and applications, from mobile phones to cars and heavy-duty Mobile Working Machines (MWM). This thesis is a summary of work focus on the utilization of IMUs for state estimation of MWM. Inertial sensor-based technology oļ¬€ers an alternative to the traditional solution, since it can signiļ¬cantly decrease the system cost and improve its robustness. For covering the research topic of whole-body estimation with IMUs, ļ¬ve publications focus on the development of novel algorithms, which use sensor fusion or rotary IMU theory to estimate or calculate the states of MWM. The test-platforms are also described in detail. First, we used low-cost IMUs installed on the surface of a hydraulic arm to estimate the joint state. These robotic arms are installed on a ļ¬‚oating base, and the joints of the arms rotate in a two-dimensional (2D) plane. The novel algorithm uses an Extended Kalman Filter (EKF) to fuse the output of the gyroscopes and the accelerometers, with gravity as the reference. Second, a rotary gyroscope is mounted on a grasper of a crane, and the rotary gyroscope theory is implemented to decrease the drift of the angular velocity measurement. Third, low-cost IMUs are attached to the wheels and the bogie test bed, and the realization of IMU-based wheel odometry is investigated. Additionally, the rotary gyroscope provides information about the roll and yaw attitude for the test bed. Finally, we used an industry grade IMU fuse with the output of wheel odometry to estimate the position and attitude of the base for an MWM moving on slippery ground. One of the main aims of this research study is to estimate the states of an MWM only using IMU sensors. The research achievements indicate this approach is promising. However, the observability of IMU in the yaw direction of the navigation frame is limited so it is diļ¬ƒcult to estimate the yaw angle of the rotation plane for the robotic arm when only using IMUs, to ensure the long-term reliable yaw angle and position of the vehicle base, external information might also be needed. When applying the rotary IMU theory, minimization of the power supply for the rotation device is still a challenge. This research study demonstrates that IMUs can be low-cost and reliable replacements for traditional sensors in joint angle measurement and in the wheel rotation angle for vehicles, among other applications. An IMU can also provide a robust state for a vehicle base in a challenging environment. These achievements will beneļ¬t future developments of MWMs in remote control and autonomous operations

    Continuous maintenance and the future ā€“ Foundations and technological challenges

    Get PDF
    High value and long life products require continuous maintenance throughout their life cycle to achieve required performance with optimum through-life cost. This paper presents foundations and technologies required to offer the maintenance service. Component and system level degradation science, assessment and modelling along with life cycle ā€˜big dataā€™ analytics are the two most important knowledge and skill base required for the continuous maintenance. Advanced computing and visualisation technologies will improve efficiency of the maintenance and reduce through-life cost of the product. Future of continuous maintenance within the Industry 4.0 context also identifies the role of IoT, standards and cyber security

    Yksivapausasteisen joustavan hydraulirobotin mallinnus ja sƤƤtƶ

    Get PDF
    The use of lighter construction materials is desirable in robotic arms and manipulators alike due to their cost advantage and high payload to weight ratio. Lightweight materials also lead to increasing structural flexibility, which induces challenges to the control problem of endpoint positions of flexible arms. This is caused by the complex dynamics of flexible links. In this thesis a single-link flexible beam was studied, which is a part of a 1-degree-of-freedom assembly, actuated by a hydraulic cylinder. The beam's dimensions are 60x60x3 mm and its length is 4.5 m, while a load mass of 60 kg is bolted near the tip. Therefore, the system at hand is highly flexible. The objective of this thesis was to build and implement a VDC (Virtual Decomposition Control) type controller to the system and test its performance. The VDC approach is a model-based, nonlinear control method, developed especially for robots with high numbers of degrees-of-freedom. The VDC approach is subsystem based, enabling individual control of each of the subsystems. The dynamics of each subsystem remain relatively simple, no matter how complex the entire robot is. A finite element model of the boom was also created in order to simulate the system before real-time implementation. The FEM (Finite Element Method) is a popular method in modeling structural flexibility. The VDC controller was implemented with success. The L2 and Linf stabilities of the subsystems were mathematically shown, leading to the guaranteed stability of the entire system. The results of this thesis show promise in the use of the VDC approach in controlling flexible arms with hydraulic actuation

    DEVELOPMENT OF A KINETIC MODEL FOR STEERABLE CATHETERS FOR MINIMALLY INVASIVE SURGERY

    Get PDF
    The steerable catheters have demonstrated many advantages to overcome the limitations of the conventional catheters in the minimally invasive surgery. The motion and force transmission from the proximal end to distal tip of the catheter have significant effects to the efficiency and safety of surgery. While the force information between the catheter and the body (e.g., vessel) can be obtained by mounting sensors on the distal tip of the catheter, this would be more intrusive and less reliable than the one without the sensors, which is described in this disseration. In addition, the small diameters of the catheters may also restrict the idea of mounting sensors on the distal tip. The other approach to obtain the force information is to infer it from the information outside the body. This will demand an accurate mathematical model that describes the force and motion relation called kinetic model, and unfortunately, such a kinetic model is not available in the literature. In this dissertation, a kinetic model for steerable catheters is presented wich captures the following characteristics of the steerable catheter, namely (1) the geometrical non-linear behavior of the catheter in motion, (2) the deformable pathway, (3) the friction between the catheter and the pathyway, and (4) the contact between the catheter and pathway. A non-linear finite element system (SPACAR) was employed to capture these characteristics. A test-bed was built and an experiment was carried out to verify the developed kinetic model. The following conclusions can be drawn from this dissertation: (1) the developed kinetic model is accurte in comparison with those in literature; (2) the Dahl friction model, the LuGre friction model and the simplified LuGre friction model are able to capture the friction behavior between the catheter and the pathway but the Coulomb friction model fails (as it cannot capture the hysteresis property which has a significant influence on the behavior of the catheter); (3) the developed kinetic model has the potential of being used to optimize the design and operation of steerable catheters with several salient findings that (3a) the maximal contact force between the catheter and the pathway occurs on the tip of the distal part or the connecting part between the distal part and catheter body of the catheter and (3b) the rigidity and length of the distal part are crucial structural parameters that affect the motion and force transmission significantly. There are several contributions made by this dissertation. In the field of the steerable catheter, biomechanics and bio-instrumentation, the contributions are summarized in the following: (1) the approach to develop the kinetic model of the steerable catheter in a complex work environment is useful to model other similar compliant medical devices, such as endoscope; (2) the kinetic model of the steerable catheter can provide the force information to improve the efficiency and safety of MIS (minimally invastive surgery) and to realize the ā€œdoctor-assistedā€ catheter-based MIS procedure; (3) the kinetic model can provide accurate data for developing other simplified models for the steerable catheters in their corresponding work environments for realizing the robotic-based fully automated MIS procedure. (4) The kinetic model of the steerable catheter and the test-bed with the corresponding instruments and methods for the kinetic and kinematic measurements are a useful design validation in the steerable catheter technology as well as for the training of physicians to perform the catheter-based interventional procedure by adding more complex anatomic phantoms. In the field of continuum manipulator and continuum robots, the approach to develop the kinetic model is useful to model other manipulators and robots, such as snake-like robots

    Improving Automated Operations of Heavy-Duty Manipulators with Modular Model-Based Control Design

    Get PDF
    The rapid development of robotization and automation in mobile working machines aims to increase productivity and safety in many industrial sectors. In heavy-duty applications, hydraulically actuated manipulators are the common solution due to their large power-to-weight ratio. As hydraulic systems can exhibit nonlinear dynamic behavior, automated operations with closed-loop control become challenging. In industrial applications, the dexterity of operations for manipulators is ensured by providing interfaces to equip product variants with diļ¬€erent tool attachments. By considering these domain-speciļ¬c tool attachments for heavy-duty hydraulic manipulators (HHMs), the autonomous robotic operating development for all product variants might be a time-consuming process. This thesis aims to develop a modular nonlinear model-based (NMB) control method for HHMs to enable systematic NMB model reuse and control system modularity across diļ¬€erent HHM product variants with actuators and tool attachments. Equally importantly, the properties of NMB control are used to improve the high-performance control for multi degrees-of-freedom robotic HHMs, as rigorously stability-guaranteed control systems have been shown to provide superior performance. To achieve these objectives, four research problems (RPs) on HHM controls are addressed. The RPs are focused on damping control methods in underactuated tool attachments, compensating for static actuator nonlinearities, and, equally signiļ¬cantly, improving overall control performance. The fourth RP is introduced for hydraulic series elastic actuators (HSEAs) in HHM applications, which can be regarded as supplementing NMB control with the aim of improving force controllability. Six publications are presented to investigate the RPs in this thesis. The control development focus was on modular NMB control design for HHMs equipped with diļ¬€erent actuators and tool attachments consisting of passive and actuated joints. The designed control methods were demonstrated on a full-size HHM and a novel HSEA concept in a heavy-duty experimental setup. The results veriļ¬ed that modular control design for HHM systems can be used to decrease the modiļ¬cations required to use the manipulator with diļ¬€erent tool attachments and ļ¬‚oating-base environments
    • ā€¦
    corecore