Narrow Results

A systematic methodology for solving the inverse dynamics of a 6-PRRS parallel robot is presented. Based on the principle of virtual work and the Lagrange approach, a methodology for deriving the dynamical equations of motion is developed. To resolve the inconsistency between complications of established dynamic model and real-time control, a simplifying strategy of the dynamic model is presented. The dynamic character of the 6-PRRS parallel robot is analyzed by example calculation, and a full and precise dynamic model using simulation software is established. Verification results show the validity of the presented algorithm, and the simplifying strategies are practical and efficient.

In this work, the design, analysis, and characterization of a parallel robotic motion generation platform with 6-degrees of freedom (DoF) for magnetic resonance imaging (MRI) applications are presented. The motivation for the development of this robot is the need for a robotic platform able to produce accurate 6-DoF motion inside the MRI bore to serve as the ground truth for motion modeling; other applications include manipulation of interventional tools such as biopsy and ablation needles and ultrasound probes for therapy and neuromodulation under MRI guidance. The robot is comprised of six pneumatic cylinder actuators controlled via a robust sliding mode controller. Tracking experiments of the pneumatic actuator indicates that the system is able to achieve an average error of 0.69 $\pm$ 0.14mm and 0.67 $\pm$ 0.40mm for step signal tracking and sinusoidal signal tracking, respectively. To demonstrate the feasibility and potential of using the proposed robot for minimally invasive procedures, a phantom experiment was performed in the benchtop environment, which showed a mean positional error of 1.20 $\pm$ 0.43mm and a mean orientational error of 1.09 $\pm 0.57^{\circ }$, respectively. Experiments conducted in a 3T whole body human MRI scanner indicate that the robot is MRI compatible and capable of achieving positional error of 1.68 $\pm$ 0.31mm and orientational error of 1.51 $\pm$ 0.32^∘ inside the scanner, respectively. This study demonstrates the potential of this device to enable accurate 6-DoF motions in the MRI environment.

Robot-assisted surgery is an active interdisciplinary field. Conventional surgical robots are mostly serial architectures, which have the advantages of large workspace, high dexterity and maneuverability. The disadvantages are low stiffness and poor positioning accuracy compared to the parallel structure robots.

This paper presents the development of a parallel surgical robot for precise skull drilling in stereotactic neurosurgical operations. The dimensions of this robot are 35 × 35 × 45 cm³, and its weight is about 6 kg. This surgical robot has 6° of freedom. The feed carriage of the bone drilling device mounted the parallel surgical robot provides one additional translational degree of freedom. A master-slave microcontroller-based system is designed for pose control. In applications for neurosurgical operation, the workspace is on the surface of a skull located at one side of the robot. This work analyzed asymmetric workspace on the surface of a sphere representing the skull. A special socket joint design that enlarges the asymmetric workspace of the robot for about 30% is also proposed.

This parallel surgical robot has been integrated with an automatic bone drilling carriage developed in our previous work to achieve completely automatic bone drilling.

As an auxiliary treatment, the 6-DOF parallel robot plays an important role in lower limb rehabilitation. In order to improve the efficiency and flexibility of the lower limb rehabilitation training, this paper studies the impedance controller based on the position control. A nonsingular terminal sliding mode control is developed to ensure the trajectory tracking precision and in contrast to traditional PID control strategy in the inner position loop, the system will be more stable. The stability of the system is proved by Lyapunov function to guarantee the convergence of the control errors. Simulation results validate the effectiveness of the target impedance model and show that the parallel robot can adjust gait trajectory online according to the human-machine interaction force to meet the gait request of patients, and changing the impedance parameters can meet the demands of different stages of rehabilitation training.