Chenkun Qi

Spatially Constrained Fuzzy-Clustering-Based Sensor Placement for Spatiotemporal Fuzzy-Control System

Many industrial processes are spatiotemporal dynamic systems. A three-dimensional fuzzy-logic controller (3-D FLC) has been recently developed to process the inherent capability of spatiotemporal dynamic systems. Sensor placement, which is always crucial to the control of spatiotemporal dynamic systems, is also critical to the design of the 3-D FLC. In this paper, a new sensor-placement strategy is developed. Its main feature is to position the sensor by utilizing the main characteristics of spatial distribution. The key technique is to use a spatial-constrained fuzzy c-means algorithm to extract the characteristics of spatial distribution. For an easy implementation, a systematic sensor-placement design scheme in four steps (i.e., data collection, dimension reduction, data clustering, and sensor locating) is developed. Finally, control of a catalytic packed-bed reactor is taken as an application to demonstrate the effectiveness of the proposed sensor-placement scheme.

Human-Tracking Strategies for a Six-legged Rescue Robot Based on Distance and View

Human tracking is an important issue for intelligent robotic control and can be used in many scenarios, such as robotic services and human-robot cooperation. Most of current human-tracking methods are targeted for mobile/tracked robots, but few of them can be used for legged robots. Two novel human-tracking strategies, view priority strategy and distance priority strategy, are proposed specially for legged robots, which enable them to track humans in various complex terrains. View priority strategy focuses on keeping humans in its view angle arrange with priority, while its counterpart, distance priority strategy, focuses on keeping human at a reasonable distance with priority. To evaluate these strategies, two indexes(average and minimum tracking capability) are defined. With the help of these indexes, the view priority strategy shows advantages compared with distance priority strategy. The optimization is done in terms of these indexes, which let the robot has maximum tracking capability. The simulation results show that the robot can track humans with different curves like square, circular, sine and screw paths. Two novel control strategies are proposed which specially concerning legged robot characteristics to solve human tracking problems more efficiently in rescue circumstances.

Gait planning for a quadruped robot with one faulty actuator

Fault tolerance is essential for quadruped robots when they work in remote areas or hazardous environments. Many fault-tolerant gaits planning method proposed in the past decade constrained more degrees of freedom(DOFs) of a robot than necessary. Thus a novel method to realize the fault-tolerant walking is proposed. The mobility of the robot is analyzed first by using the screw theory. The result shows that the translation of the center of body(CoB) can be kept with one faulty actuator if the rotations of the body are controlled. Thus the DOFs of the robot body are divided into two parts: the translation of the CoB and the rotation of the body. The kinematic model of the whole robot is built, the algorithm is developed to actively control the body orientations at the velocity level so that the planned CoB trajectory can be realized in spite of the constraint of the faulty actuator. This gait has a similar generation sequence with the normal gait and can be applied to the robot at any position. Simulations and experiments of the fault-tolerant gait with one faulty actuator are carried out. The CoB errors and the body rotation angles are measured. Comparing to the traditional fault-tolerant gait they can be reduced by at least 50%. A fault-tolerant gait planning algorithm is presented, which not only realizes the walking of a quadruped robot with a faulty actuator, but also efficiently improves the walking performances by taking full advantage of the remaining operational actuators according to the results of the simulations and experiments.

A quadruped robot with parallel mechanism legs

Summary form only given. The design and control of quadruped robots has become a fascinating research field because they have better mobility on unstructured terrains. Until now, many kinds of quadruped robots were developed, such as JROB-1 [1], BISAM [2], BigDog [3], LittleDog [4], HyQ [5] and Cheetah cub [6]. They have shown significant walking performance. However, most of them use serial mechanism legs and have animal like structure: the thigh and the crus. To swing the crus in swing phase and support the bodys weight in stance phase, a linear actuator is attached on the thigh [2, 3, 5, 6], or instead, a rotational actuator is installed on the knee joint [1, 4]. To make the robot more useful in the wild environment, e.g., the detection or manipulation tasks, the payload capability is very important. To carry the sensors or tools, heavy load legged robot is very necessary. Thus the knee actuator should be lightweight, powerful and easy to maintain. However, this can be very costly and hard to satisfy at the same time.

A fuzzy-based spatio-temporal multi-modeling for nonlinear distributed parameter processes

Many industrial processes belong to nonlinear distributed parameter systems (DPS) with significant spatio-temporal dynamics. They often work at multiple operating points due to different production and working conditions. To obtain a global model, the direct modeling and experiments in a large operating range are often very difficult. Motivated by the multi-modeling, a fuzzy-based spatio-temporal multi-modeling approach is proposed for nonlinear DPS. To obtain a reasonable operating space division, a priori information and the fuzzy clustering are used to decompose the operating space from coarse scale to fine scale gradually. To get a smooth global model, a three-domain (3D) fuzzy integration method is proposed. Using the proposed method, the model accuracy will be improved and the experiments become easier. A fuzzy-based spatio-temporal multi-modeling approach is proposed for modeling nonlinear distributed parameter processes.To obtain a reasonable operating space division, a priori information and the fuzzy clustering are used to decompose the operating space from coarse scale to fine scale gradually.To get a smooth global model, a three-domain (3D) fuzzy integration method is proposed.Using the proposed method, the model accuracy will be improved and the experiments become easier. Many industrial processes belong to nonlinear distributed parameter systems (DPS) with significant spatio-temporal dynamics. They often work at multiple operating points due to different production and working conditions. To obtain a global model, the direct modeling and experiments in a large operating range are often very difficult. Motivated by the multi-modeling, a fuzzy-based spatio-temporal multi-modeling approach is proposed for nonlinear DPS. To obtain a reasonable operating space division, a priori information and the fuzzy clustering are used to decompose the operating space from coarse scale to fine scale gradually. To reduce the dimension in the local spatio-temporal modeling, the Karhunen-Loeve method is used for the space/time separation. Both multi-modeling and space/time separation can reduce the modeling complexity. Finally, to get a smooth global model, a three-domain (3D) fuzzy integration method is proposed. Using the proposed method, the model accuracy will be improved and the experiments become easier. The effectiveness is verified by simulations.

A Novel Identification Methodology for the Coordinate Relationship between a 3D Vision System and a Legged Robot

Coordinate identification between vision systems and robots is quite a challenging issue in the field of intelligent robotic applications, involving steps such as perceiving the immediate environment, building the terrain map and planning the locomotion automatically. It is now well established that current identification methods have non-negligible limitations such as a difficult feature matching, the requirement of external tools and the intervention of multiple people. In this paper, we propose a novel methodology to identify the geometric parameters of 3D vision systems mounted on robots without involving other people or additional equipment. In particular, our method focuses on legged robots which have complex body structures and excellent locomotion ability compared to their wheeled/tracked counterparts. The parameters can be identified only by moving robots on a relatively flat ground. Concretely, an estimation approach is provided to calculate the ground plane. In addition, the relationship between the robot and the ground is modeled. The parameters are obtained by formulating the identification problem as an optimization problem. The methodology is integrated on a legged robot called “Octopus”, which can traverse through rough terrains with high stability after obtaining the identification parameters of its mounted vision system using the proposed method. Diverse experiments in different environments demonstrate our novel method is accurate and robust.

Compensation of Velocity Divergence Caused by Dynamic Response for Hardware-in-the-Loop Docking Simulator

The hardware-in-the-loop simulation on the ground is effective to test the contact dynamics of the spacecraft in space. However, it is very challenging due to the simulation velocity divergence caused by the time delay. In this study, a compensation approach for the velocity divergence caused by the dynamic response of the motion simulator is proposed. Traditional delay compensation requires the time delay or the delay model to be known. In practice, the dynamic response of the motion simulator is time varying and unknown. This motivates development of the model-free compensation approach. It compensates the contact force from the real-time response error of the motion simulator and the real-time identified contact stiffness and damping. The proposed compensation approach is easy to implement since it does not require the dynamic response model of the motion simulator. Simulations and experiments are used to verify the effectiveness of the proposed compensation approach.

Modelling and trajectory planning for a four legged walking robot with high payload

This paper illustrates the development of a new four legged walking machine. The robot is characterized by a high payload capacity; the result has been achieved according to the specific design of its actuation system, integrating novel high precision actuators, and to its legs, composed by a new family of parallel mechanisms characterized by an appreciable dexterity. With respect to the common walking robot, the particular design of the hydraulic cylinders does not let neglect the weight of the legs in terms of static stability. Hence, a strategy to optimize the whole robot behaviour has been developed. More specifically, the modelling operation and the simulations performed to optimize some quasi-static tasks have been analysed. The optimization process employs a Global Search Algorithm that provides the best results in terms of Stable Margin. The same optimization procedure has been applied with success to investigate the robot walking gait.

Obstacle avoidance and motion planning scheme for a hexapod robot Octopus-III

Abstract Legged robots have advanced potential to move in complex environment accomplishing operating, rescuing and detecting tasks. In real applications, bypassing large obstacles is a more common choice for legged robots comparing with walking over and climbing the obstacles. However, few papers involve the obstacle avoidance approach for legged robots. An obstacle avoidance and motion planning scheme for a hexapod robot is presented in this paper. The scheme takes advantage of the superior mobility of the legged robot and fulfills requirements of walking stability and kinematic feasibility. Firstly, a novel obstacle avoidance trajectory planning method is proposed, which is inspired by the superior mobility of the legged robot. Then, a motion generation approach for the legged robot is developed to control the robot to walk along the planned trajectory. The approach coordinates the body motion and the feet motions to fulfill requirements of walking stability and kinematic feasibility simultaneously. Finally, the scheme is integrated on a hexapod robot and tested by real experiments.

A Force Compensation Approach Toward Divergence of Hardware-in-the-Loop Contact Simulation System for Damped Elastic Contact

The simulation of contact process of flying objects in space is important for many space missions. The hardware-in-the-loop (HIL) simulation is an attractive approach because it integrates the fidelity of physical simulation and the flexibility of numerical simulation. But the HIL contact simulation is divergent due to the time delay, e.g., the dynamic response delay and the force measurement delay. In this study, a force compensation approach is proposed toward the HIL simulation divergence problem for the damped and elastic contact. The idea is to make the compensated force close to the ideal force corresponding to the numerical position computed from the dynamics model of flying objects. The approach includes the phase lead based force compensation for the force measurement delay, and the response error based force compensation for the dynamic response delay of the motion simulator. From simulations and experiments, it is shown that the proposed approach can effectively and satisfactorily compensate the simulation divergence.