An integrated localization-navigation scheme for distance-based docking of UAVs

In this paper we study the distance-based docking problem of unmanned aerial vehicles (UAVs) by using a single landmark placed at an arbitrarily unknown position. To solve the problem, we propose an integrated estimation-control scheme to simultaneously achieve the relative localization and navigation tasks for discrete-time integrators under bounded velocity: a nonlinear adaptive estimation scheme to estimate the relative position to the landmark, and a delicate control scheme to ensure both the convergence of the estimation and the asymptotic docking at the given landmark. A rigorous proof of convergence is provided by invoking the discrete-time LaSalle's invariance principle, and we also validate our theoretical findings on quadcopters equipped with ultra-wideband ranging sensors and optical flow sensors in a GPS-less environment

Psychometric Properties of the Chinese version of UPPS-P Impulsive Behavior Scale.

OBJECTIVE: The present study aimed to assess the psychometric properties of a Chinese version of the UPPS-P Impulsive Behavior Scale. The associations between the UPPS-P scale and impulsivity choice, gender, smoking, and drinking status were also assessed. METHODS: A total of 127 adults ranging from 21 to 65 years old participated in the study. Participants were administered with the Chinese version of the UPPS-P Impulsive Behavior Scale, Beck Depression Inventory II (BDI-II), and State-Trait Anxiety Inventory (STAI). Impulsivity choice tasks were also tested including the Delay Discounting Task (DDT), Balloon Analogue Risk Task (BART), and Beads Task (Beads). RESULTS: A new version of the UPPS-P Impulsive Behavior Scale was formed that includes 40 items. The scores of the UPPS-P Impulsive Behavior Scale demonstrated adequate internal consistency on five subscales but less sufficient structure validity in the present sample. In addition, positive urgency was negatively related to the Beads task; negative urgency and positive urgency were positively related to the DDT and BART. Moreover, positive and negative urgency were positively correlated with depression; all five subscales were positively correlated with anxiety; sensation seeking was higher in males than females and in alcohol drinkers than non-drinkers; and lack of premeditation and lack of perseverance were higher in nonsmokers than smokers. CONCLUSIONS: The present study supports the reliability but not the structure validity of the UPPS-P Impulsive Behavior Scale. The impulsivity personality trait assessed by the UPPS-P scale was associated with impulsivity choice, depression, anxiety, gender, and drinking and smoking status. Further studies should be conducted to explore the structure of impulsivity in the Chinese population

Distributed multi-agent consensus under constraints

As a basic problem in the cooperative control of multi-agent systems (MASs), distributed multi- agent consensus aims to achieve an agreement of certain interested variables among a group of agents by exchanging information between neighbors. It has found a variety of engineering applications in different areas, e.g. coordination, rendezvous, flocking and formation control. To implement consensus in practice, we need to consider different kinds of constraints. On the one hand, practical MASs bear their own physical limits, such as limited communication bandwidth and kinematic constraints; on the other hand, the final consensus value needs to satisfy further requirements in some specific tasks. This thesis is dedicated to the study of two specific consensus problems under constraints: quantized consensus under data rate constraint, and optimal consensus under set or kinematic constraints. The first part of the thesis considers the quantized consensus problem under data rate constraint. In a multi-agent network, any communication channel has limited capacity and only finite bits of error-free information can be transmitted per unit time. As a result, the consensus protocol is designed in the presence of quantized signals and limited data rate. Although the result on using finite bits of data exchange to achieve quantized consensus for MASs with some general linear dynamics has been established, it is still an open problem about how many bits of data suffice to achieve consensus for systems with high-order dynamics and a partially measured state, and it is not clear what determines the sufficient data rate for consensus In this work, we focus on the quantized consensus for two kinds of critical high-order dynamics: n-th order integrators (n ≥ 3), and 2m-th order oscillators (m ≥ 1) with m identical pairs of conjugate poles on the unit circle. Besides, in either case only the first state variable is measurable. We design an observer-based dynamic encoding-decoding scheme to estimate the unmeasurable state variables, and devise a control protocol based on the encoder/decoder outputs. By employing perturbation techniques, we are able to explicitly design the control gains and provide a sufficient data rate for quantized consensus. Under a fixed and connected network, for MASs with integrator dynamics it only needs n bits of information exchange to achieve exponentially fast consensus, while for oscillator dynamics the number of required bits is an integer between m and 2m, which is dependent on the location of poles, or the oscillation frequency. These results not only achieve the lowest data rate among existing works, but also indicate that the sufficient data rate is independent of the network topology, and closely related with the system structure. The second part of the thesis considers the optimal consensus problem under set or kinematic constraints. The optimal consensus aims to achieve an agreement of state that minimizes the aggregate cost, which is the sum of individual costs assigned to each agent. A typical example is the shortest-distance rendezvous, which may be further required to be achieved within a given constraint set. Continuous-time MASs with single integrator dynamics are first studied. To achieve the constrained optimum, we combine three different terms into the control protocol: local averaging, local projection, and local subgradient descent with a decaying gain α(t). Under a balanced network with uniformly joint spanning trees, we employ non-smooth analysis to show that the convergence to the constrained optimum set can be guaranteed if α(t) is non-integrable. Provided that the aggregate cost is strongly convex, we further analyze the convergence rate for different types of α(t). In a similar vein, we establish corresponding results for discrete-time systems, and further discuss the necessary conditions and the issue of communication delay when the balanced network is fixed. We also explore the optimal consensus under kinematic constraints, specifically for MASs with hererogeneous EL dynamics under bounded input and velocity. Assuming an exact knowledge of nonlinearity and a priori estimate of the optimum, we show that an exponentially fast convergence is guaranteed while satisfying the bounded kinematic constraints, if the fixed and undirected topology is connected.Doctor of Philosophy (EEE

Relative docking via range-only measurements

This paper studies the problem of range-based relative docking of a single robot. In particular, we propose an integrated localization and navigation scheme for a robot to navigate itself to a desired relative displacement w.r.t. a fixed landmark at an unknown position, where the proposed controllers only require distance and odometry measurements. Instead of using a single range measurement as an indicator of the proximity to the desired docking point in existing works, the main idea of this work is to construct additional artificial anchors along the robot's motion trajectory first and then adopt the measurements corresponding to these anchors as the indicator. It is proved that the proposed controller will navigate the robot to the desired docking position asymptotically given proper parameter settings. Two simulation examples are presented to demonstrate the effectiveness of our theoretical results.Nanyang Technological UniversityNational Research Foundation (NRF)Accepted versio

Relative docking and formation control via range and odometry measurements

This article studies the problem of distance-based relative docking of a single robot and formation control of multirobot systems. In particular, an integrated localization and navigation scheme is proposed for a robot to navigate itself to a desired relative position with respect to a fixed landmark at an unknown position, where only range and odometry measurements are used. By carefully embedding historical measurements into equilibrium conditions, we design an integrated estimation-control scheme to achieve the relative docking asymptotically. It is rigorously proved that the robot will converge to the desired docking position asymptotically provided that control gains are chosen to satisfy certain conditions. This scheme is further extended to multirobot systems to consider an integrated relative localization and formation control problem. Unlike widely used spatial cooperation in the existing literature, we propose to exploit both spatial and temporal cooperations for achieving formation control. It is proved that multirobot formation can be achieved with zero error for directed acyclic graphs. Several simulation examples are provided to validate our theoretical results.Nanyang Technological UniversityNational Research Foundation (NRF)Accepted versio

Psychometric Properties of the Chinese version of UPPS-P Impulsive Behavior Scale.

The present study aimed to assess the psychometric properties of a Chinese version of the UPPS-P Impulsive Behavior Scale. The associations between the UPPS-P scale and impulsivity choice, gender, smoking, and drinking status were also assessed. A total of 127 adults ranging from 21 to 65 years old participated in the study. Participants were administered with the Chinese version of the UPPS-P Impulsive Behavior Scale, Beck Depression Inventory II (BDI-II), and State-Trait Anxiety Inventory (STAI). Impulsivity choice tasks were also tested including the Delay Discounting Task (DDT), Balloon Analogue Risk Task (BART), and Beads Task (Beads). A new version of the UPPS-P Impulsive Behavior Scale was formed that includes 40 items. The scores of the UPPS-P Impulsive Behavior Scale demonstrated adequate internal consistency on five subscales but less sufficient structure validity in the present sample. In addition, positive urgency was negatively related to the Beads task; negative urgency and positive urgency were positively related to the DDT and BART. Moreover, positive and negative urgency were positively correlated with depression; all five subscales were positively correlated with anxiety; sensation seeking was higher in males than females and in alcohol drinkers than non-drinkers; and lack of premeditation and lack of perseverance were higher in nonsmokers than smokers. The present study supports the reliability but not the structure validity of the UPPS-P Impulsive Behavior Scale. The impulsivity personality trait assessed by the UPPS-P scale was associated with impulsivity choice, depression, anxiety, gender, and drinking and smoking status. Further studies should be conducted to explore the structure of impulsivity in the Chinese population