736 publications from this institution
To solve the local trap problems in traditional mobile robot navigation strategy, a algorithm is proposed for mobile robot based on a sonar ring to realize the navigation in an unknown and complex environment. An obstacle avoidance behavior based on Fuzzy logic control and wall-following are presented on the base of building models of sonar data. Using FSM(finite state machine), the navigation status of mobile robot transfer when the information of environment changes, and a corresponding strategy is chosen to realize the navigation task. This algorithm can effectively solve the local trap problems in traditional mobile robot navigation strategy. Experiments on the Pioneer 3DX mobile robot are conducted to evaluate the performance of the algorithm, and good results are obtained.
This paper described a pilot study and two follow-up experiments, using a device developed in the laboratory to study the human fingertip's discrimination and memory for softness perception. According to the pilot study, soft objects were easier to identify than hard ones. When subjects touched objects, the number of times seemed to be from 2 to 6. For most, the touch frequency ranged from 0.3 to 1.3 Hz. In Exp. 1, the method of constant stimuli was used to study the human fingertip's stiffness difference threshold for haptic perception. The estimated difference threshold averaged over 24 subjects was 33 N/m. And, the stiffness difference thresholds for most people were in the range of 20 N/m to 40 N/m. In Exp. 2, the haptic memory span was discussed according to the recall experiment. Human haptic memory span lay between three and four items.
The fractional differential algorithm has a good effect on extracting image textures, but it is usually necessary to select an appropriate fractional differential order for textures of different scales, so we propose a novel approach for haptic texture rendering of two-dimensional (2D) images by using an adaptive fractional differential method. According to the fractional differential operator defined by the Grünvald–Letnikov derivative (G–L) and combined with the characteristics of human vision, we propose an adaptive fractional differential method based on the composite sub-band gradient vector of the sub-image obtained by wavelet decomposition of the image texture. We apply these extraction results to the haptic display system to reconstruct the three-dimensional (3D) texture force filed to render the texture surface of two-dimensional (2D) images. Based on this approach, we carry out the quantitative analysis of the haptic texture rendering of 2D images by using the multi-scale structural similarity (MS-SSIM) and image information entropy. Experimental results show that this method can extract the texture features well and achieve the best texture force file for 2D images.
To realize the quantitative analysis and research of traditional Chinese medicine (TCM) acupuncture manipulations, miniaturized multidimensional force sensors are necessary to measure the lifting–thrusting force and twisting torque in the process of acupuncture, which records the manipulations of excellent physicians for relevant physicians to learn and improve their manipulations. A miniature multiaxis force/torque ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${F}/{T}$ </tex-math></inline-formula> ) sensor for acupuncture is developed in this article. The elastomer of the design adopts hollow thin-wall cross beam structure with inverted <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${T}$ </tex-math></inline-formula> floating beam, which retains the space for the strain gauge to be pasted, reduces the coupling between dimensions, and improves the sensitivity and accuracy. This design has the advantages of miniaturization, lightweight, high precision, and convenient needle substitution. The elastomer is processed with polyetheretherketone (PEEK) material to reduce the mass. First, the feasibility of the hollow thin-wall cross beam structure with inverted <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${T}$ </tex-math></inline-formula> floating beam is verified by ANSYS finite element simulation. Then, the hardware system based on STM32 is designed to realize signal acquisition, amplification, and transmission. Next, the static calibration and decoupling of the sensor are accomplished with the calibration device. The calibration results indicate that the accuracy of the sensor is high (the coupling error is less than 2%). Finally, the acupuncture force measurement system is constructed to complete the acupuncture manipulation experiment. The experimental results demonstrate that our system can accurately obtain the needle force information and can distinguish different acupuncture manipulations, which verifies the feasibility of the sensor while realizing the quantitative characterization of acupuncture manipulations.
In this paper, two novel adaptive finite-time control schemes are proposed for position tracking of nonlinear teleoperation system, which dynamic uncertainties, actuator saturation, and time-varying communication delays are considered. First, a novel auxiliary variable is designed to provide more stable performance. The radial basis function (RBF) neural network is introduced to estimate dynamic uncertainties. Second, two adaptive finite-time control schemes are investigated. In control scheme I, the RBF neural network and the gain switching strategy are applied to compensate the actuator saturation. In control scheme II, an auxiliary compensation filter and the compensation adaptive update laws, which contain the finite-time structure, are developed for dealing with saturation. Third, the finite-time adaptive controller is designed in each of these two control schemes. Based on the multiple Lyapunov function method, the closed-loop teleoperation system with these two control methods is proved to be bounded and finite-time stability. Finally, the simulation experiments are performed and the comparisons with other control methods are shown. The effectiveness of the proposed control schemes is demonstrated.
The brain-machine interface (BMI) has been reported to offer the potential for controlling the assistive robot for the motor impaired people, using the non-invasively obtained electroencephalogram (EEG) signals. However, the EEG based BMI may not be sufficient and stable to drive the robot moving freely in its 2D or 3D workspace. The robot autonomy may provide assistance for the BMI users with the shared control paradigm. Nevertheless, users suffers from several limitations of the current shared control paradigms applied on BMI, e.g., loss of sense of control, high mental workload due to unintuitive control with the human-robot interface and fixed level of assistance. To overcome these drawbacks, we propose a new control paradigm for the robotic arm reaching task where the robot autonomy is dynamically blended with the gaze-BMI control from a user. In this paradigm, the hybrid gaze-BMI constitutes an intuitive and effective input to continuously control the robotic arm end-effector moving freely in its 2D workspace, with an adjustable speed proportional to the motion intention strength. Furthermore, the adjustable level of assistance by our paradigm allows the system to balance the user's capabilities and feelings of control while compensating for the reaching task's difficulty. The proposed paradigm is verified in the task where a healthy subject utilizes the hybrid gaze-BMI to control the robotic arm end-effector reaching for a target object while avoiding the obstacle in the path. The experimental results demonstrate that the movements with our shared control paradigm are safer, more efficient and less difficult than those without shared control.
An improved discrete mass-spring model is proposed for modeling of deformation of soft object. And the algorithm to realize real-time force reflection to the human operator based on this model is given with suitable parameters. Finally, the experiment demonstrates that this novel physics based deformation model has the properties of high accuracy and quick computational speed by comparison with other deformation models.