ModLab UPenn the modular robotics laboratory at the university of pennsylvania

Chao Liu

Chao Liu
Position: Ph.D Student

Research Interests: Motion Planning and Control

Office: Perch

Email: chaoliu at

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A Quadratic Programming Approach to Manipulation in Real-Time

Manipulation tasks usually involve the control of redundant robots to reach large workspaces while avoiding obstacles and satisfying other constraints. This results in motion planning in high-dimensional space. In addition, whole-body manipulation tasks using multi-limbed robots may need the control of more than one manipulators. Modular robots can be used to construct many useful morphologies […]

Motion Planning for Variable Topology Truss Modular Robot

Featured on! Variable topology truss (VTT) is a self-reconfigurable modular truss robot. Similar to other types of truss robots, a VTT is composed of multiple members or edge modules which are the beam elements in the truss and nodes that are the connections among members, and can achieve high structural efficiency, change its shape […]

A Fast Configuration Space Algorithm for Variable Topology Truss Modular Robots

Variable topology truss (VTT) is a modular robotic system which is composed of multiple edge modules including a linear actuator as the truss member plus the two ends of the member that attach or detach from other ends to form the node. A VTT usually has at least 18 actuated degrees-of-freedom (DOFs) and typically more […]

Spiral Zipper Manipulator for Aerial Grasping and Manipulation

We present a novel manipulator for aerial vehicles to perform grasping and manipulation tasks. The goal is to design a low-cost, relatively light but strong manipulator with a large workspace and compact storage space that can be mounted on an unmanned aerial system. A novel design solution based on the Spiral Zipper, an expanding tube, […]

Variable Topology Truss

Variable Topology Trusses (VTT) are a new class of self-reconfigurable robot. A VTT consists of linear actuators for the truss members, which are joined at the truss nodes by a special reconfigurable spherical joint. The VTT can reconfigure by merging and splitting these truss nodes.

Reconfiguration Motion Planning for Variable Topology Truss

Finalist for Best Paper Award on Safety, Security, and Rescue Robotics in Memory of Motohiro Kisoi at IROS 2019 This work presents an algorithm to do motion planning for a new class of self-reconfigurable modular robot: the variable topology truss (VTT). Modular robots consist of many modules that can be configured into various structures, and […]

A Distributed Reconfiguration Planning for Modular Robots

Self-reconfigurable modular robots are usually composed of multiple modules with uniform docking interfaces that can be transformed into different configurations by themselves. The reconfiguration planning problem is finding what sequence of reconfiguration actions are required for one arrangement of modules to transform into another. We present a novel reconfiguration planning algorithm for modular robots. The […]

Configuration Recognition with Distributed Information for Modular Robots

Modular robots are usually composed of multiple blocks with uniform docking interfaces that can be transformed into different configurations. It is a significant challenge to recognize modular robot configurations composed of hundreds of modules. Given a new configuration, it is important to match it to an existing configuration and, if true, map each module to […]

Tether-Tube Robots

Tether-Tube Robot are a new type of parallel robots constructed from tethers and tubes. It is similar to cable robots but, rather than just using cables, expanding tubes are also used to do actuation. This design is achieved by utilizing a novel prismatic joint called Spiral Zipper developed in ModLab.


The PaintPot manufacturing process is a new way to create low-cost, low-profile, highly customizable potentiometers for position sensing in robotic applications. It uses widely accessible materials, requires no special expertise, and creates custom potentiometers in a variety of shapes and sizes, including curved surfaces.

The EP-Face Connector

We present the EP-Face connector, a novel connector for hybrid chain-lattice type modular robots that is high- strength (88.4N), compact, fast, power efficient, and robust to position errors.


SMORES-EP is a modular robot designed and built at the University of Pennsylvania, and used by researchers at Penn and Cornell. SMORES standsĀ for Self-Assembling MOdular Robot for Extreme Shapeshifting, and EP refers to the Electro-Permanent magnets the modules use to connect.

Low-cost Laser Range Finder

The goal for this project is to make a low-cost but high-speed , very small and reliable laser range finder. The idea is to talk to a small camera, and obtain the laser line position and send out the data line by line in real-time.


Our mobile telepresence robot is fitted with a robotic manipulator that will allow a person to virtually manipulate the avatar environment. We have shown our robot called "Persona" to be capable of moving up and down ramps, use elevators, manipulate objects such as chess pieces, and to lift and transport loads up to 4.5 kg.