Degree Of Freedom Robot Research Articles

Performance of Robotic Assistance for Skull Base Biopsy: A Phantom Study.

Objectives This study aims to evaluate the feasibility of a custom robot system guided by optical cone beam computed tomography (CBCT)-based navigation for skull base biopsy. Design An accuracy study was conducted. Setting Platform for navigation and robot-aided surgery technology. Participants Phantom skull. Main Outcome Measures The primary outcome measure was to investigate the accuracy of robot-assisted needle biopsy for skull base tumors. A 14-gauge needle was automatically inserted by the five degrees of freedom robot into the intended target, guided by optical navigation. The result was displayed on the graphical user interface after matrix transformation. Postoperative image scanning was performed, and the result was verified with image fusion. Results All 20 interventions were successfully performed. The mean deviation of the needle tip was 0.56 ± 0.22 mm (measured by the navigation system) versus 1.73 ± 0.60 mm (measured by image fusion) ( p < 0.05). The mean insertion depth was 52.3 mm (range: 49.7-55.2 mm). The mean angular deviations off the x-axis, y-axis, and z-axis were 1.51 ± 0.67, 2.33 ± 1.65, and 1.47 ± 1.16 degrees, respectively. Conclusions The experimental results show the robot system is efficient, reliable, and safe. The navigation accuracy is a significant factor in robotic procedures.

Design optimization method for 7 DOF robot manipulator using performance indices

This paper proposes an optimal design method for the design parameters that affect the performance of 7 degrees of freedom (DOF) serial manipulators. The proposed method optimizes the manipulator parameters by using performance indices related to the distribution of inertia, while considering the workspaces and dexterity that correspond to the kinematic performance, and the energy that corresponds to the dynamic performance. The Structural Length Index (SLI) and Global Conditioning Index (GCI), which are kinematic performance indices, and the Modified Dynamic Conditioning Index (MDCI), which is a dynamic performance index, were used as objective functions. After deriving the parameters that affect manipulator performance through these performance indices, a Genetic Algorithm was used for the optimization. This method should be helpful in theoretically designing those parameters that have been created by relying on experience, thus far, in the initial conceptual design stage in 7 DOF manipulator designs.

Appearance learning for 3D pose detection of a satellite at close-range

In this paper we present a learning-based 3D detection of a highly challenging specular object exposed to a direct sunlight at very close-range. An object detection is one of the most important areas of image processing, and can also be used for initialization of local visual tracking methods. While the object detection in 3D space is generally a difficult problem, it poses more difficulties when the object is specular and exposed to the direct sunlight as in a space environment. Our solution to a such problem relies on an appearance learning of a real satellite mock-up based on a vector quantization and the vocabulary tree. Our method, implemented on a standard computer (CPU), exploits a full perspective projection model and provides near real-time 3D pose detection of a satellite for close-range approach and manipulation. The time consuming part of the training (feature description, building the vocabulary tree and indexing, depth buffering and back-projection) are performed offline, while a fast image retrieval and 3D-2D registration are performed on-line. In contrast, the state of the art image-based 3D pose detection methods are slower on CPU or assume a weak perspective camera projection model. In our case the dimension of the satellite is larger than the distance to the camera, hence the assumption of the weak perspective model does not hold. To evaluate the proposed method, the appearance of a full scale mock-up of the rear part of the TerraSAR-X satellite is trained under various illumination and camera views. The training images are captured with a camera mounted on six degrees of freedom robot, which enables to position the camera in a desired view, sampled over a sphere. The views that are not within the workspace of the robot are interpolated using image-based rendering. Moreover, we generate ground truth poses to verify the accuracy of the detection algorithm. The achieved results are robust and accurate even under noise due to specular reflection, and able to initialize a local tracking method.

Comparison of Techniques for Disturbance-Tolerant Position Control of the Manipulator of PUMA Robot using PID

Objectives: The control of the robotic manipulator arm under a variety of faults has been studied and the performance is compared using PID and other technique. Methods/Statistical Analysis: In a highly nonlinear environment such as manipulator of a robot, employing more than one control techniques yields desirable results. Here, a combination of PID along with pole-placement control of linear model has been designed. The feedback control gains have been obtained offline using equivalent linearization of the nonlinear coupled robot dynamic system. The input torque has been obtained from PID. The combined torque has been applied to the joints. This scheme has been implemented online in a standard PUMA manipulator with the payload. Findings: It has been observed that PID as compared to modified pole placement method is more efficient to control a robotic arm. Application/Improvement: The proposed hybrid control approach involving offline designs and their online implementation on six degrees of freedom robot has been found to be efficient and capable of accommodating common types of faults represented as an exponential or sine or a constant function but sudden or abrupt in nature.

Robotic system with multiplex power transmission for MRI-guided percutaneous interventions.

In minimally invasive prostate percutaneous interventions, Magnetic Resonance Imaging (MRI) compatible robotic assistive systems developed over the years tend to have multiple degrees of freedom (DOF) to accomplish complex surgical tasks. This paper presents a novel design of an MRI-compatible transmission that allows one driving motor to control a multiplexed DOF robot system. The transmission could reduce the number of motors in the system, while maintaining the functionality of the system, by controlling each motion sequentially rather than simultaneously. A series of preliminary experiments as well as a targeting accuracy test are conducted to evaluate the accuracy of the system.

Research on Optimization Walking Robot Gait Planning Based on Human Bionics

This paper had analyzed the degree of freedom robot and then simulates the robots and humans similar to the lower limbs, to establish sports model of the robot. The analysis robot has 10 degrees of freedom, in which one leg has five degrees of freedom, namely, a degree of freedom of the knee, hip ankle is assigned two degrees of freedom. Depending on the needs of the kinematic model is divided into forward motion model and lateral movement model. Link by representatives’ form various parts of the robot to simplify the model. Through the establishment of the geometry and the Cartesian coordinate system, analyze the relationship between the joint angle and joint use mathematical functions to represent the correspondence between swing foot and between each joint. By Zero Moment Point (ZMP) stability analysis, to ensure the stability of humanoid robot, obtained center of gravity and zero moment point formula, thus proving humanoid robot walking stability. Using of spline interpolation and polynomial fitting method for solving the hip, the equations of motion of the ankle joint, the knee. By setting the parameters, the use of MATLAB simulation software to obtain motion curve of each joint and humanoid robot designed to simulate obtain humanoid robot gait simulation video.

SU‐G‐JeP3‐03: Effect of Robot Pose On Beam Blocking for Ultrasound Guided SBRT of the Prostate

Purpose:Ultrasound presents a fast, volumetric image modality for real‐time tracking of abdominal organ motion. How‐ever, ultrasound transducer placement during radiation therapy is challenging. Recently, approaches using robotic arms for intra‐treatment ultrasound imaging have been proposed. Good and reliable imaging requires placing the transducer close to the PTV. We studied the effect of a seven degrees of freedom robot on the fea‐sible beam directions.Methods:For five CyberKnife prostate treatment plans we established viewports for the transducer, i.e., points on the patient surface with a soft tissue view towards the PTV. Choosing a feasible transducer pose and using the kinematic redundancy of the KUKA LBR iiwa robot, we considered three robot poses. Poses 1 to 3 had the elbow point anterior, superior, and inferior, respectively. For each pose and each beam starting point, the pro‐jections of robot and PTV were computed. We added a 20 mm margin accounting for organ / beam motion. The number of nodes for which the PTV was partially of fully blocked were established. Moreover, the cumula‐tive overlap for each of the poses and the minimum overlap over all poses were computed.Results:The fully and partially blocked nodes ranged from 12% to 20% and 13% to 27%, respectively. Typically, pose 3 caused the fewest blocked nodes. The cumulative overlap ranged from 19% to 29%. Taking the minimum overlap, i.e., considering moving the robot's elbow while maintaining the transducer pose, the cumulative over‐lap was reduced to 16% to 18% and was 3% to 6% lower than for the best individual pose.Conclusion:Our results indicate that it is possible to identify feasible ultrasound transducer poses and to use the kinematic redundancy of a 7 DOF robot to minimize the impact of the imaging subsystem on the feasible beam directions for ultrasound guided and motion compensated SBRT.Research partially funded by DFG grants ER 817/1‐1 and SCHL 1844/3‐1.

Development of an embedded control system by means of dsPIC applied in a 4 DOF robot

In this paper the design and implementation of an embedded control system, using DSCs (Digital Signal Controller) devices of dsPIC type, applied on a four DOF (Degrees Of Freedom) robotic manipulator OWI-535 model is presented. The mathematical model of manipulator is elaborated obtaining joint trajectories to achieve the tracking of a test Cartesian trajectory. A control structure based on a Master/Slave configuration, between two dsPIC30F4013 through SPI (Serial Peripheral Interface) protocol is developed. In such a system, algorithms are implemented: PID (Proportional Integral Derivative) with anti-windup and, generation PWM (Pulse-Width Modulation) and data acquisition, in the DSCs master and slave, respectively. The results are exposed by comparative curves between the desired and real joint trajectories and joint error graphs, generated from real data of the implementation.

Dual objective motion planning subject to state constraints

SUMMARYThis paper presents a novel motion planning approach inspired by the Dynamic Programming (DP) applicable to multi degree of freedom robots (mobile or stationary) and autonomous vehicles. The proposed discrete–time algorithm enables a robot to reach its destination through an arbitrary obstacle field in the fewest number of time steps possible while minimizing a secondary objective function. Furthermore, the resulting optimal trajectory is guaranteed to be globally optimal while incorporating state constraints such as velocity, acceleration, and jerk limits. The optimal trajectories furnished by the algorithm may be further updated in real time to accommodate changes in the obstacle field and/or cost function. The algorithm is proven to terminate in a finite number of steps without its computational complexity increasing with the type or number of obstacles. The effectiveness of the global and replanning algorithms are demonstrated on a planar mobile robot with three degrees of freedom subject to velocity and acceleration limits. The computational complexity of the two algorithms are also compared to that of an A*–type search.

The Role of the Anterolateral Structures and the ACL in Controlling Laxity of the Intact and ACL-Deficient Knee

Background: Anterolateral rotatory instability (ALRI) may result from combined anterior cruciate ligament (ACL) and lateral extra-articular lesions, but the roles of the anterolateral structures remain controversial. Purpose: To determine the contribution of each anterolateral structure and the ACL in restraining simulated clinical laxity in both the intact and ACL-deficient knee. Study Design: Controlled laboratory study. Methods: A total of 16 knees were tested using a 6 degrees of freedom robot with a universal force-moment sensor. The system automatically defined the path of unloaded flexion/extension. At different flexion angles, anterior-posterior, internal-external, and internal rotational laxity in response to a simulated pivot shift were tested. Eight ACL-intact and 8 ACL-deficient knees were tested. The kinematics of the intact/deficient knee was replayed after transecting/resecting each structure of interest; therefore, the decrease in force/torque reflected the contribution of the transected/resected structure in restraining laxity. Data were analyzed using repeated-measures analyses of variance and paired t tests. Results: For anterior translation, the intact ACL was clearly the primary restraint. The iliotibial tract (ITT) resisted 31% ± 6% of the drawer force with the ACL cut at 30° of flexion; the anterolateral ligament (ALL) and anterolateral capsule resisted 4%. For internal rotation, the superficial layer of the ITT significantly restrained internal rotation at higher flexion angles: 56% ± 20% and 56% ± 16% at 90° for the ACL-intact and ACL-deficient groups, respectively. The deep layer of the ITT restrained internal rotation at lower flexion angles, with 26% ± 9% and 33% ± 12% at 30° for the ACL-intact and ACL-deficient groups, respectively. The other anterolateral structures provided no significant contribution. During the pivot-shift test, the ITT provided 72% ± 14% of the restraint at 45° for the ACL-deficient group. The ACL and other anterolateral structures made only a small contribution in restraining the pivot shift. Conclusion: The ALL and anterolateral capsule had a minor role in restraining internal rotation; the ITT was the primary restraint at 30° to 90° of flexion. Clinical Relevance: The ITT showed large contributions in restraining anterior subluxation of the lateral tibial plateau and tibial internal rotation, which constitute pathological laxity in ALRI. In cases with ALRI, an ITT injury should be suspected and kept in mind if an extra-articular procedure is performed.

Medial Subluxation of the Tibia After Anterior Cruciate Ligament Rupture as Revealed by Standing Radiographs and Comparison With a Cadaveric Model

Background: Biomechanical studies indicate that the tibia shifts medially and has a more valgus orientation in the anterior cruciate ligament (ACL)–deficient knee. However, it is not known whether these differences can be detected on standing radiographs. Purpose: To determine whether medial subluxation and more changes in coronal alignment of the tibia are detectable in both weightbearing radiographs and a cadaveric model simulating quiet standing. Study Design: Case series; Level of evidence, 4, and Descriptive laboratory study. Methods: Radiographic data were available for a cross-section of 74 patients with unilateral ACL tears. Tibial subluxation and coronal limb alignment were measured on hip-to-ankle weightbearing radiographs. Eight cadaveric knees were mounted on a 6 degree of freedom robot. Mediolateral position and varus-valgus alignment of the tibia relative to the femur were measured in response to 300-N axial compression simulating quiet standing at 5° and 15° of flexion with the ACL intact and sectioned. Results: Across all 74 patients included in the clinical study, the ACL-injured knee experienced 1.6 ± 2.3 mm (mean ± SD) of medial tibial subluxation compared with the contralateral uninjured knee (P < .001). The 24 patients with isolated ACL rupture exhibited 2.0 ± 1.8 mm of medial subluxation (P < .001). The mean coronal alignment of all 74 patients in the study was 0.7° ± 2.8° varus in the injured limb and 1.3° ± 2.6° varus in the uninjured contralateral limb (P = .0187). In the cadaveric model, the tibia translated 0.4 ± 0.5 mm more medially after sectioning of the ACL at 15° of flexion (P = .0485); however, no changes in coronal alignment were detected. Conclusion: The tibia shifts medially and is less varus in the ACL-deficient knee on standing radiographs. The medial tibial shift is reproduced in an axially loaded cadaveric model. Clinical Relevance: Medial tibiofemoral subluxation seen on frontal plane standing radiograph is an underappreciated sequela of isolated ACL rupture. The ability of ACL reconstruction to restore this aspect of ACL injury is not well understood and should be investigated further. Cadaveric models may be used to directly measure the mechanical effect of subtle changes in mediolateral position on articular contact stress as an indicator of the importance of this finding.

An algorithm for the welding torch weaving control of arc welding robot

The teaching learning method is generally applied in six DOF (degrees of freedom) robot programming. However, for complicated weaving welding, there is a drawback using this method. That is that numerous teaching control points are needed in the programming. Based on the theory of coordinate transformation, the purpose of this paper was to address this drawback by utilizing an algorithm for the welding torch weaving control. This algorithm includes the novel formulation to calculate the tracking position, and can produce an accurate and continuous weaving path along various weld lines. The teaching programming can easily determine these weld lines which contain few teaching points. Therefore, this algorithm can reduce the programming time for the robotic welding application. A lot of experiments have been done to validate the algorithm. The experimental results show that the weaving control algorithm is correct and can produce various weaving paths.DOI: http://dx.doi.org/10.5755/j01.eee.21.2.5919

A Recipe for Soft Fluidic Elastomer Robots.

This work provides approaches to designing and fabricating soft fluidic elastomer robots. That is, three viable actuator morphologies composed entirely from soft silicone rubber are explored, and these morphologies are differentiated by their internal channel structure, namely, ribbed, cylindrical, and pleated. Additionally, three distinct casting-based fabrication processes are explored: lamination-based casting, retractable-pin-based casting, and lost-wax-based casting. Furthermore, two ways of fabricating a multiple DOF robot are explored: casting the complete robot as a whole and casting single degree of freedom (DOF) segments with subsequent concatenation. We experimentally validate each soft actuator morphology and fabrication process by creating multiple physical soft robot prototypes.

Experimental study on stand-alone assistive suspension system to reduce load on small robot manipulating heavy payload

This paper presents a single degree of freedom suspension system to assist small six degree of freedom robots manipulating heavy payload. The goal of the system is to reduce the load applied to the last link of a robot manipulating a payload that is heavier than the robot’s specified allowable load capacity. An assistive suspension system was implemented to realize vertical-only motion of the robot. A mathematical model was derived, and a proportional-integral-derivative controller with an inner velocity loop was designed. Variable parameters in the model such as friction coefficients were identified in an experiment on the voltage input and velocity output. To determine how much the assistive system reduces the load on the robot, the system was connected to the robot using an interface attached with magnets and a force sensor was fixed to the last link of the robot. In the experiment, the cable tension was measured and controlled to satisfy the design preference for the assistive system to be stand-alone, rather than relying on force sensor on the robot. The experiment was performed using various control gains under different conditions, such as the periods of input motion and payload weight. The results showed that the system could reduce 3.8 and 6.0 kg payloads on the robot to 50% and 40%, respectively.

Control of the coupled motion of a 6 DoF robotic arm and a continuum manipulator for the treatment of pelvis osteolysis.

The paper addresses the coupled motion of a 6 degree of freedom robot and a snake-like dexterous manipulator (SDM) designed for the treatment of bone defects behind the implant during total hip arthroplasty revision surgery. We have formulated the problem as a weighted, multi-objective constraint, linear optimization. A remote center of motion (RCM) acts as a virtual constraint for the robot. The coupled robot kinematics does not assume piecewise-constant curvature for the SDM. We have evaluated our method by simulating the coupled system inside a potential lesion area.

Parameter identification for industrial robots with a fast and robust trajectory design approach

Model-based, torque-level control can offer precision and speed advantages over velocity-level or position-level robot control. However, the dynamic parameters of the robot must be identified accurately. Several steps are involved in dynamic parameter identification, including modeling the system dynamics, joint position/torque data acquisition and filtering, experimental design, dynamic parameters estimation and validation. In this paper, we propose a novel, computationally efficient and intuitive optimality criterion to design the excitation trajectory for the robot to follow. Experiments are carried out for a 6 degree of freedom (DOF) Staubli TX-90 robot. We validate the dynamics parameters using torque prediction accuracy and compare to existing methods. The RMS errors of the prediction were small, and the computation time for the new, optimal objective function is an order of magnitude less than for existing approaches. HighlightsWe propose a fast, robust trajectory design for use in parameter identification.Computation time for our design is approximately 1/20 the time for prominent, existing methods.We estimate the dynamic parameters for a 6 DOF robot, the Staubli Tx-90, which has not previously been identified, to our knowledge.The RMS errors of the torque prediction were small (< 24 Nm).

ACL Fibers Inserting on the Lateral Intercondylar Ridge Carry the Greatest Loads - Are Modern Anatomic Femoral Tunnel Positions Too Low?

Objectives:Histological studies have shown that the ACL has a direct and indirect insertion on the femur [1]. The direct insertion is located along the lateral intercondylar ridge and the indirect insertion is located ‘lower’ on the lateral wall of the notch. The trend towards anatomic ACL reconstruction using the anteromedial (AM) portal technique has resulted in ‘lower’ non-isometric femoral tunnel positions and increased graft failures [2]. To our knowledge, the load transfer properties of the direct and indirect ACL insertions have not been studied. This information may help in understanding the increased failures reported with AM portal drilling. The purpose of this study was, 1) to compare the load transferred across the native ACL at the direct and indirect femoral insertions and, 2) to determine the strain behavior of ACL grafts placed at different tunnel locations within the direct and indirect insertions.Methods:Ten fresh-frozen cadaveric knees (mean age, 52.5 years; range, 29-65) were mounted to a six degree of freedom robot. A 134N anterior load at 30 and 90° flexion and a combined valgus (8Nm) and internal (4Nm) rotational moment at 15° flexion were applied. The ACL was subsequently sectioned at the femoral footprint by detaching either the direct or indirect insertion (partially sectioned state), followed by the remainder of the ACL (completely sectioned state) (Figure 1). The kinematics of the intact knee were replayed after each stage of sectioning to determine the loads transferred across the direct and indirect ACL fibers. Loads were expressed as a percentage of the total load borne by the ACL. Strain behaviour was tested by generating 3D models of the femur and tibia from CT scans of each knee. Three tunnel locations (anteromedial bundle [AM], center [C], posterolateral bundle [PL]) each were selected for the direct and indirect insertions and a virtual ACL graft was inserted. The isometry of the virtual graft was calculated through a flexion path of 0 to 90°.Results:Under an anterior tibial load at 30° flexion, the direct insertion carried 83.9% of the total ACL load compared to 16.1% in the indirect insertion (p<0.001). The direct insertion also carried more load at 90° flexion (95.2% vs 4.8%; p<0.001). Under a combined rotatory load at 15° flexion, the direct insertion carried 84.2% of the total ACL load compared to 15.8% in the indirect insertion (p<0.001). A virtual ACL graft placed at the AM position in the direct insertion demonstrated the best strain behaviour with a mean 10.9% change in length. This value was significantly lower (p<0.001) than the isometry at all 3 tunnel positions in the indirect insertion (AM = 18.5%; C = 24.9%; PL = 30.9%).Conclusion:Fibers in the direct insertion of the ACL carry more load than fibers in the indirect insertion. Virtual ACL grafts placed in the ‘higher’ direct location are more isometric than in the ‘lower’ indirect location during range of motion testing.Clinical Relevance:‘Low’ ACL grafts in the indirect ACL insertion, resulting from AM portal drilling techniques, may experience higher loads in-vivo due to unfavorable biomechanics. With the current shift towards anatomic ACL reconstruction, it may be beneficial to create a ‘higher’ femoral tunnel within the direct insertion at the lateral intercondylar ridge. This position remains anatomical but may also be biomechanically favorable.

Structure Design and Analysis of a Compact Breast Biopsy Robot under MRI Environment

Because of its excellent image quality, magnetic resonance imaging (MRI), as a new means of image guidance for breast biopsy robot, is used widely in clinical diagnostics and advanced breast research. However, the robot for MRI-guided biopsy is challenging due to the compatibility caused by strong magnetic field and very limited available space inside MR scanner. In this paper, a five degrees of freedom (DOF) robot is presented to perform biopsy in the breast with MRI guidance for the early detection of breast cancer. In an MR scanner (1.5T), the compatibility of copper, A4 non-magnetic stainless steel and POM, nylon, teflon is tested, and analyze the influence on the image of water model. Based on the analysis of available space, a 5 DOF robot which consists of 3-DOF Cartesian motions, 1-DOF rotation and 1-DOF insertion is designed, and the statics analysis of the robot is simulated using ANSYS. The results of statics analysis demonstrate that the robot meet the requirement of stiffness and precision.

Towards fully automatic reliable 3D acquisition: From designing imaging network to a complete and accurate point cloud

This paper describes a novel system for accurate 3D digitization of complex objects. Its main novelties can be seen in the new approach, which brings together different systems and tools in a unique platform capable of automatically generating an accurate and complete model for an object of interest. This is performed through generating an approximate model of the object, designing a stereo imaging network for the object with this model and capturing the images at the designed postures through exploiting an inverse kinematics method for a non-standard six degree of freedom robot. The images are then used for accurate and dense 3D reconstruction using photogrammetric multi-view stereo method in two modes, including resolving scale with baseline and with control points. The results confirm the feasibility of using Particle Swarm Optimization in solving inverse kinematics for this non-standard robot. The system provides this opportunity to test the effect of incidence angle on imaging network design and shows that the matching algorithms work effectively for incidence angle of 10°. The accuracy of the final point cloud generated with the system was tested in two modes through a comparison with a dataset generated with a close range 3D colour laser scanner.

Development of a neural controller applied in a 5 DOF robot redundant

In this paper the development of a neural controller implemented in a five Degrees Of Freedom (DOF) redundant robot is presented. The design of the control law considers the robotic system inverse model, including the performance of the actuators for the five joints, obtained through a feedforward neural network with backpropagation learning algorithm. This inverse structure is weighted by desired acceleration and derivative proportional feedback loops to provide the appropriate supply voltage to the servo motors of the robotic manipulator. Tracking tests are performed to a path in Cartesian space using a simulator developed using MatLab/Simulink software tools. It assesses the neural controller performance versus classical computed torque controller, comparing the results of curves in the joint space and Cartesian through RMS errors indices of Cartesian and joint positions.