Kun Cao

Nanyang Technological University | ntu · School of Electrical and Electronic Engineering

In this article, we consider the problem of using a multirobot system to conduct sweep coverage over a region with uneven and unknown workload distribution. Uneven workload distribution means that a robot has to spend different amounts of time covering a unit area at different locations in the region. Unknown workload distribution means that the am...

This paper presents an in-depth analytical and empirical assessment of the performance of DoubleBee, a novel hybrid aerial–ground robot. Particularly, the dynamic model of the robot with ground contact is analyzed, and the unknown parameters in the model are identified. We apply an unscented Kalman filter-based approach and a least square-based app...

Despite recent progress in trajectory planning for multiple robots and a single tethered robot, trajectory planning for multiple tethered robots to reach their individual targets without entanglements remains a challenging problem. In this article, a complete approach is presented to address this problem. First, a multirobot tether-aware representa...

Path planning for multiple tethered robots is a challenging problem due to the complex interactions among the cables and the possibility of severe entanglements. Previous works on this problem either consider idealistic cable models or provide no guarantee for entanglement-free paths. In this work, we present a new approach to address this problem...

Path planning for multiple tethered robots is a challenging problem due to the complex interactions among the cables and the possibility of severe entanglements. Previous works on this problem either consider idealistic cable models or provide no guarantee for entanglement-free paths. In this work, we present a new approach to address this problem...

This article investigates the similar formation control problem for multirobot systems. Specifically, we propose an integrated relative localization and similar formation control scheme to navigate multirobot systems to a desired configuration, which is a similar transformation of a given template, based on interrobot and robot-landmark range measu...

In this paper, we present the dynamic model and control of DoubleBee, a novel hybrid aerial-ground vehicle consisting of two propellers mounted on tilting servo motors and two motor-driven wheels. DoubleBee exploits the high energy efficiency of a bicopter configuration in aerial mode, and enjoys the low power consumption of a two-wheel self-balanc...

This paper proposes a new unified inverse reinforcement learning (IRL) framework based on trust-region methods and a recently proposed Pontryagin differential programming (PDP) method in Jin et al. (2020), which aims to learn the parameters in both the system model and the cost function for three types of problems, namely, $N$ -player nonzero-sum...

Despite recent progress on trajectory planning of multiple robots and path planning of a single tethered robot, planning of multiple tethered robots to reach their individual targets without entanglements remains a challenging problem. In this paper, we present a complete approach to address this problem. Firstly, we propose a multi-robot tether-aw...

Other than the relative position-based and bearing-based localization with aligned coordinate frames on all sensor nodes, the existing 3D network localization algorithms using distance/bearing/angle measurements without aligned coordinate frames usually require each node to have at least four neighbors, which poses large communication burden for th...

This brief proposes a game-theoretic inverse reinforcement learning (GT-IRL) framework, which aims to learn the parameters in both the dynamic system and individual cost function of multistage games from demonstrated trajectories. Different from the probabilistic approaches in computer science community and residual minimization solutions in contro...

This letter introduces a differential dynamic programming (DDP) based framework for polynomial trajectory generation for differentially flat systems. In particular, instead of using a linear equation with increasing size to represent multiple polynomial segments as in literature, we take a new perspective from state-space representation such that t...

This article studies the problem of distributed framework matching (FM), which originates from the assignment task in multirobot coordination and the matching task in pattern recognition. The objective of distributed FM is to distributively seek a correspondence which minimizes some metrics describing the disagreement between two frameworks (i.e.,...

This paper considers the scenario where multiple robots collaboratively cover a region in which the exact distribution of workload is unknown prior to the operation. The workload distribution is not uniform in the region, meaning that the time required to cover a unit area varies at different locations of the region. In our approach, we divide the...

This paper studies the distributed localization problem of d-dimensional (d=2,3) sensor networks using local bearing measurements. Firstly, a distributed algorithm for computing barycentric coordinates in both 2-D and 3-D sensor networks is proposed where only local bearing measurements are required. Secondly, some necessary and/or sufficient condi...

This paper introduces a differential dynamic programming (DDP) based framework for polynomial trajectory generation for differentially flat systems. In particular, instead of using a linear equation with increasing size to represent multiple polynomial segments as in literature, we take a new perspective from state-space representation such that th...

In this paper, cooperative circumnavigation (CCN) is studied for groups of networked unmanned aerial vehicles (UAVs) under a directed interaction topology. The CCN drives UAVs to given planar ellipses with desired spatial formation. A first contribution is that based on affine transformations, CCN control design is structured, which can deploy UAVs...

This paper studies the problem of distance-based relative docking of a single robot and formation control of multi-robot 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 odom...

This paper develops a Bearing-Ratio-of-Distance (B-RoD) rigidity theory to study when a framework can be uniquely determined by a set of B-RoD constraints up to directly similar transformation (translation, positive scaling). In particular, a framework is specified by a set of B-RoD constraints, i.e., mixed bearing and RoD measurements (the ratio o...

This paper develops a Ratio-of-Distance (RoD) rigidity theory to study when a framework can be uniquely determined by a set of RoD constraints up to similar transformations (translation, rotation, scaling and reflection). In particular, a framework is specified by a set of RoD constraints (the ratio of distances of a pair of edges joining a common...

This paper studies the dynamic formation control problem for cooperative agents with discrete-time dynamics over directed graphs. Unlike using absolute coordinate, relative coordinate, interagent distance, or interagent bearing to specify the target formation and coordinate agents to achieve the formation, we study a coordination problem where the...

Continuum robots have excited increasing attention and efforts from the robotic community due to their high dexterity and safety. This paper proposes a design for a type of multimodule continuum robot equipped with an elastic backbone structure and tendon-driven actuation system. The kinematic model of the robot is formulated where the maximum bend...