YouTube Channel: https://www.youtube.com/channel/UCifbz0OjcLNfh8IKUEQIcVQ/videos 

Serial and Cable-Driven Parallel Robots (CDPRs) are two types of robots that are widely used in industrial applications. Usually, the former offers high position accuracy at the cost of high motion inertia and small workspace envelope. The latter has a large workspace, low motion inertia, and high motion accelerations, but low accuracy. In this research, redundant Hybrid Cable-Driven Robots (HCDRs) are proposed to harness the strengths and benefits of serial and CDPRs. Although the study has been directed at warehousing applications, the developed techniques are general and can be applied to other applications (e.g., applied in biomimetics/rehabilitation/medicine/industry).

The main goal of this research is to develop integrated control systems to reduce vibrations and improve the position accuracy of HCDRs. For the proposed HCDRs, the research includes system modeling, redundancy resolution, optimization problem formulation, integrated control system development, and simulation and experimental validation.

In this research, first, a generalized HCDR is proposed for the step-by-step derivation of a generic model, and it can be easily extended to any HCDRs. Then, based on an in-plane configuration, three types of control architecture are proposed to reduce vibrations and improve the position accuracy of HCDR. Their performance is evaluated using several well-designed case studies. Furthermore, a stiffness optimization algorithm is developed to overcome the limitations of existing approaches.

Decoupled system modeling is studied to reduce the complexity of HCDRs. Control design, simulations, and experiments are developed to validate the models and control strategies. Additionally, state estimation algorithms are proposed to overcome the inaccurate limitation of Inertial Measurement Unit (IMU). Based on these state observers, experiments are conducted in different cases to evaluate the control performance.

An Underactuated Mobile Manipulator (UMM) is proposed to address the tracking and vibration- and balance-control problems. Out-of-plane system modeling, disturbance analysis, and model validation are also investigated. Besides, a simple but effective strategy is developed to solve the equilibrium point and balancing problem. Based on the dynamic model, two control architectures are proposed. Compared to other Model Predictive Control (MPC)-based control strategies, the proposed controllers require less effort to implement in practice. Simulations and experiments are also conducted to evaluate the model and control performance.

Finally, redundancy resolution and disturbance rejection via torque optimization in HCDRs are proposed: joint-space Torque Optimization for Actuated Joints (TOAJ) and joint-space Torque Optimization for Actuated and Unactuated Joints (TOAUJ). Compared to TOAJ, TOAUJ can solve the redundancy resolution problem as well as disturbance rejection. The algorithms are evaluated using a Three-Dimensional (3D) coupled HCDR and can also be extended to other HCDRs.

The main contributions of this work are as follows: (1) General system modeling for HCDRs; (2) Redundancy resolution and optimization problem formulation in HCDRs;(3) Integrated control system development for HCDRs.

• Ronghuai Qi, Amir Khajepour, and William W. Melek, “Redundancy Resolution and Disturbance Rejection via Torque Optimization in Hybrid Cable-Driven Robots (HCDRs),” IEEE Transactions on Systems, Man and Cybernetics: Systems, In press.

• Ronghuai Qi, Amir Khajepour, and William W. Melek, “Modeling, Tracking, Vibration and Balance Control of an Underactuated Mobile Manipulator (UMM),” Control Engineering Practice, vol. 93, pp. 104159, 2019.  PDF  Video

• Ronghuai Qi, Mitchell Rushton, Amir Khajepour, and William W. Melek, “Decoupled Modeling and Model Predictive Control of a Hybrid Cable-Driven Robot,” Robotics and Autonomous Systems, vol. 118, pp. 1–12, 2019.  PDF  Video 1  Video 2

• Ronghuai Qi, Amir Khajepour, and William W. Melek, “Generalized Flexible Hybrid Cable-Driven Parallel Robot: Modeling, Control, and Analysis,” IEEE Transactions on Systems, Man and Cybernetics: Systems, Under Review.  arXiv

• Ronghuai Qi, Amir Khajepour, and William W. Melek, “Kinematically Constrained Hybrid Cable-Driven Parallel Robots (HCDPRs): Modeling, Vibration Control, and Trajectory Tracking,” ASME Journal of Mechanisms and Robotics, Under Review.

• Ronghuai Qi, Redundant Hybrid Cable-Driven Robots: Modeling, Control, and Analysis, PhD thesis, University of Waterloo, Waterloo, ON, Canada, Aug. 2019.  PDF

For the study of soft robotics, I was inspired by living organisms and constructed robots from highly compliant materials for dealing with unstructured environment and dynamic tasks. My research focused on design and control to enhance robots' mobility, manipulation performance, and adaptability. 

In this research, a low-cost and lightweight inflatable robot finger is designed for safe human-robot interaction and adaptive gripping. The proposed soft inflatable robot finger is different from traditional designs. It uses a common and low cost inflatable material and can be easily and massively manufactured. The proposed soft inflatable finger only weighs 0.8 grams, but can well realize swift movement which is actuated by low pressure air. Numerous analyses and experiments have been conducted for key parameters selection of the mechanical design.

Currently, I am working on the modeling and learning-based control of modular soft grippers.

• Ronghuai Qi, Tin Lun Lam, and Yangsheng Xu, “Design and Implementation of a Low–Cost and Lightweight Inflatable Robot Finger,” in Proc. IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), Chicago, USA, Sep. 14–18, 2014, pp. 28–33.  PDF  Video

• Ronghuai Qi, et al., “A Modular Fluid-Driven Soft Gripper: Design, Characterization, Control, and Applications,” IEEE Robotics and Automation Letters, To be Submitted. 

In this research, a novel soft inflatable arm is proposed for humanoid robots. The new proposed structure of the arm is achieved by a very common and low-cost inflatable material and it is very light, weighing only about 50 g. However, it can realize agile movement by driving six tiny cables installed in the shoulder and elbow joints. The soft inflatable arm can work by pumping air at a very low pressure (7.32 ± 3.45 kPa) and allows direct and soft human contact without any external force sensors. This research proposes joint compressed models, joint kinematic models, and kinematic models for the whole inflatable robot arm. These models can be easily applied to multijoint arms. In addition, a new redundancy resolution method is also developed for the inflatable arm, which makes it easier to control resolution and is less complex than other traditional approaches. Numerous experiments have been conducted, including performances of accuracy, repeatability, motion trajectories, human-safe interaction, and remote interaction.

• Ronghuai Qi, Amir Khajepour, William W. Melek, et al., “Design, Kinematics, and Control of a Multijoint Soft Inflatable Arm for Human-Safe Interaction,” IEEE Transactions on Robotics, vol. 33, no. 3, pp. 594–609, 2017.  PDF  Video 1  Video 2

• Ronghuai Qi, Tin Lun Lam, and Yangsheng Xu, “Mechanical Design and Implementation of a Soft Inflatable Robot Arm for Safe Human–Robot Interaction,” in Proc. IEEE International Conference on Robotics and Automation (ICRA), Hong Kong, China, May 31–June 7, 2014, pp. 3490–3495.  PDF 

• Ronghuai Qi, Tin Lun Lam, and Yangsheng Xu, “Kinematic Modeling and Control of a Multi–joint Soft Inflatable Robot Arm with Cable–Driven Mechanism,” in Proc. IEEE International Conference on Robotics and Automation (ICRA), Hong Kong, China, May 31–June 7, 2014, pp. 4819–4824.  PDF

With the advancing globalization, people travel needs become more and more frequent. Nonetheless, travels spend a lot of effort, time and money, which is one of the major problems for modern urbanities. In addition, frequent use of transport also increased the carbon emissions. To cope with these problems, a Telepresence Robot is presented.

In smart cities, users in anywhere can connect remote telepresence robots via the internet and control it to move around freely and interact with people and objects. It acts as a user's real-world avatar. The application includes remote parties, meetings, consultations, school and inspection which are particularly suitable for those with busy life or mobility problems. 

To enhance users' and remote participants' telepresence experience, in addition to the capability of move, transmitting sounds and images, telepresence robot has a feature of presenting users' facial expressions and body language.

As a Project Manger and core developer, I created a project proposal and published seven patents and three software packages. The work was also reported by many media, such as China Daily Asia.