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To effectively reduce the mass and simplify the structure of traditional aerial manipulators, we propose novel light cable-driven manipulator for the aerial robots in this article. The drive motors and corresponding reducers are removed from the joints to the base; meanwhile, force and motion are transmitted remotely through cables. Thanks to this design, the moving mass has been greatly reduced. In the meantime, the application of cable-driven technology also brings about extra difficulties for high-precise control of cable-driven manipulators. Hence, we design a nonsingular terminal sliding mode controller using time-delay estimation. The time-delay estimation is applied to obtain lumped system dynamics and found an attractive model-free scheme, while the nonsingular terminal sliding mode controller is utilized to enhance the control performance. Stability is analyzed based on Lyapunov theory. Finally, the designed light cable-driven manipulator and presented time-delay estimation-based nonsingular terminal sliding mode controller are analyzed. Corresponding results show that (1) our proposed cable-driven manipulator has high load to mass ratio of 0.8 if we only consider the moving mass and (2) our proposed time-delay estimation-based nonsingular terminal sliding mode is model-free and can provide higher accuracy than the widely used time-delay estimation-based proportional–derivative (PD) controller.

To satisfy the needs of surgeons for judging the contact state of the catheter robot and modify the operation accordingly, a novel contact torque estimation and haptic feedback method is proposed in this article. Using the vibrotactile feedback, the proposed method reminds the surgeon which bending unit of the robot contacts with human tissue and guides him to realize the disengagement. Based on a novel simplification of the driving force of the robot, a quasi-statics model is established to estimate the contact torque. Simulations are conducted based on Finite Element Method (FEM) to verify the accuracy of the quasi-statics model and the estimation method. A robot system composed of a catheter robot, a PC, a master-operator, and a wearable vibration glove is assembled according to this method. To verify the feasibility of this method, a contact torque estimation experiment and a vibrotactile feedback experiment are conducted in this article. The results show that this method is accurate and effective.

To overcome the problems of structural parametric uncertainty and cable transmission model complexity, a nonlinear controller based on time-delay estimation and fuzzy self-tuning is proposed. The unknown dynamics and disturbances are estimated by time delaying the state of motion immediately before. The control gains are self-tuned by a fuzzy controller, which can reduce the errors caused by system’s uncertainties and external disturbances. Compared with the conventional Proportional-derivative (PD) and time-delay control, the result shows that the proposed control scheme based on time-delay estimation can improve the joint trajectory tracking accuracy of cable-driven robot by significantly reducing the control gains. With the PD gains self-tuned by fuzzy strategy, the mean square errors of trajectory tracking are decreased approximately by 5–20% more than the conventional time-delay control with constant gains. In addition, the experimental result shows that the proposed method has an effective inhibitory effect on dead zone in cable-driven joints. Experiment performed on position tracking control of a 2-degree-of-freedom cable-driven robot is presented to illustrate that the controller has the advantages of simple and reliable structure, model-free, strong robustness, and high tracking accuracy.

For the motion coordination problem between the underwater vehicle and manipulator of the underwater vehicle–manipulator system, a new redundancy resolution method is proposed and investigated. The proposed method mainly has two parts: a fuzzy logic part and a multitasks weighted gradient projection method part. The fuzzy logic part is used to decide the weight factors of the motion distribute matrix and the priorities of all the secondary objectives, while the multitasks weighted gradient projection method part is used to handle the secondary objectives with the weight factors and priorities decided by the fuzzy logic part. Moreover, a new secondary objective is proposed to optimize underwater vehicle–manipulator system’s attitude, which takes the payload into consideration. Finally, the effectiveness of the proposed redundancy resolution is verified through some comparative simulations.