Hi, I'm Pio Ong

I am currently a postdoctoral research associate at California Institute of Technology under the supervision of Prof. Aaron Ames. My main research focus is on the intelligent resource-aware control for nonlinear systems. I received a Bachelor's degree in Aerospace Engineering from the University of California, San Diego (UCSD) in 2012, and a Master's degree in Astronautical Engineering from University of Southern California (USC) in 2013. During Fall and Winter of 2014, I worked as an intern at Space Exploration Technologies Corp (SpaceX), which has sparked my interests in studying control theory. In 2022, I received my Ph.D. degree from UCSD, and my Ph.D. advisor was Prof. Jorge Cortés. Check out my research interests in the Research section.

Email: pioong@caltech.edu

Academic CV

News

Journal Paper Published

Our paper “Characterizing Smooth Safety Filters via the Implicit Function Theorem” is published in IEEE Control Systems Letters.

See Paper
January 2024

Journal Paper Accepted

Our paper “Performance-barrier-based event-triggered control with applications to network systems” is accepted for publication in Transactions on Automatic Control.

See Paper
October 2023

Papers Submitted

We submitted two papers to ACC 2024.

See Paper 1 See Paper 2
September 2023

Paper Accepted

The paper "Intermittent Safety Filters for Event-Triggered Safety Maneuvers with Application to Satellite Orbit Transfers" is accepted, and will be presented at CDC 2024.

See Paper
July 2023

Journal Paper Accepted

Our paper “Nonsmooth control barrier function design of continuous constraints for network connectivity maintenance” is accepted for publication in Automatica.

See Paper
June 2023

Start Teaching

My position as a lecturer at Caltech began. For the Spring quarter of 2023, I was hired to teach an undergraduate course on the introduction to controls (CDS 110/ChE 105).

April 2023

Papers Submitted

We submitted two papers to CDC 2023.

See Paper 1 See Paper 2
March 2023

Papers Accepted

Both papers we submitted to CDC 2022 get accepted.

See Paper 1 See Paper 2
September 2022

Start Postdoc

I started my post-doctoral research under the guidance of Prof. Aaron Ames at Caltech.

Prof Ames's Website
January 2022

Defended Thesis!

I successfully defended my thesis, and therefore, finished my studies at UCSD. Thank you Prof. Jorge Cortes for being an awesome advisor.

December 2021

Paper Submitted

We submitted a paper “Performance-barrier-based event-triggered control with applications to network systems” to Transactions on Automatic Control.

See Paper
August 2021

Research Interests

My broad research theme is resource conservation in control systems. For the control of dynamical systems, we use various resources to accomplish our performance goals, e.g., convergence rate in asymptotic stability and safety level in obstacle avoidance, with some diminishing return. These control resources can include, but are not limited to, actuation, estimation, computation, communication, and even human supervision. My research investigates scenarios where some of these control resources are limited. Particularly, I am interested in autonomous systems like aircraft and spacecrafts that must operate independently for an extended period of time without the ability to freely resupply resources. My vision is to equip autonomous systems with the capability to make real-time decisions on resource utilization, with the goal of reducing the overall usage while maintaining a desired level of system performance. My research will provide general sustainability solutions for the control of dynamical systems with direct applications to resource-constrained systems. My research topics include:

Event-triggered control (ETC) is a tool for accomplishing control tasks while conserving resources. Our research involves pushing the boundary on the efficiency of ETC, and at the same time, tying in performance criteria to the trigger design. In addition, we tackle unsolved problems in the area, such as Zeno-free distributed trigger design, and interesting applications of ETC, such as satellite control and human-robot interaction.

Control barrier functions (CBFs) are employed to address safety concerns, i.e., the possibilities of system trajectory to evolve to undesirable states. Our research focuses on the implementation issues of a CBF-based feedback controller. This includes both smoothness (or continuity) property and resource usage of the controller. Interesting applications of CBF we study include connectivity maintenance of a multi-robot system and safety and coordination of space systems.

Our research explores the exciting possibilities of applying novel techniques, e.g., event-triggered control and control barrier functions, to network systems in a distributed way. We use tools like graph theory and dynamic average consensus to help with analyses. Applications we look at include multi-robot systems and power systems.

Smoothness property is a desirable trait in both theories and real-world applications. For instance, we need Lipschitzness of the close-loop system in order to ensure properties like existence and uniqueness of solutions, continuity of solutions in initial conditions and parameters, etc. My research looks at undesirable nonsmoothness that may arise in typical control designs and we offer ways to eliminate such possibilities. For one work in this area, we develop our own version of Sontag's famous universal formula (for smooth controllers) that also takes into account safety criterion from a control barrier function, in addition to the Lyapunov's condition for stability.

Publications

Journal Papers

  1. M. H. Cohen, P. Ong, G.Bahati, A. D. Ames Characterizing smooth safety filters via the implicit function theorem
    IEEE Control Systems Letters, 7:3890-3895, 2024.
  2. P. Ong, J. Cortés Performance-barrier-based event-triggered control with applications to network systems
    IEEE Transactions on Automatic Control, 69(7), 2024. To appear
  3. P. Ong, B. Capelli, L. Sabattini, J. Cortés. Nonsmooth control barrier function design of continuous constraints for network connectivity maintenance
    Automatica, 156:111209, 2023
  4. A. J. Taylor, P. Ong, J. Cortés, A. D. Ames. Safety-critical event triggered control via input-to-state safe barrier functions
    IEEE Control Systems Letters 5(3):749-754, 2021
    (First two authors contributed equally to the paper)
  5. P. Ong and J. Cortés. Opportunistic robot control for interactive multiobjective optimization under human performance limitations
    Automatica 123:109253, 2021

Conference Papers

  1. G. Bahati, P. Ong, A. D. Ames. “Sample-and-hold safety with control barrier functions”
    Proceedings of the American Control Conference, Toronto, Canada, July 2024. Submitted.
  2. M. H. Cohen, P. Ong, G. Bahati, A. D. Ames. “Characterizing smooth safety filters via the implicit function theorem”
    Proceedings of the American Control Conference, Toronto, Canada, July 2024. Submitted.
  3. P. Ong, A. D. Ames. “Intermittent Safety Filters for Event-Triggered Safety Maneuvers with Application to Satellite Orbit Transfers”
    Proceedings of the IEEE Conference on Decision and Control, Marina Bay Sands, Singapore, December 2023. To appear
  4. P. Ong, G. Bahati, A. D. Ames. “Stability and safety through event-triggered intermittent control with application to spacecraft orbit stabilization”
    Proceedings of the IEEE Conference on Decision and Control, Cancun, Mexico, 2022, pp. 453-460
  5. A. J. Taylor, P. Ong, T. G. Molnar, A. D. Ames. “Safe backstepping with control barrier functions”
    Proceedings of the IEEE Conference on Decision and Control, Cancun, Mexico, 2022, pp. 5775-5782
  6. P. Ong, B. Capelli, L. Sabattini, J. Cortés. “Network connectivity maintenance via nonsmooth control barrier functions”
    Proceedings of the IEEE Conference on Decision and Control, Austin, Texas, 2021, pp. 4780-4785
    (First two authors contributed equally to the paper)
  7. A. J. Taylor, P. Ong, J. Cortés, A. D. Ames. “Safety-critical event triggered control via input-to-state safe barrier functions”
    Proceedings of the IEEE Conference on Decision and Control, Jeju Island, South Korea, 2020
    (First two authors contributed equally to the paper)
  8. P. Ong and J. Cortés. “Universal formula for smooth safe stabilization”
    Proceedings of the IEEE Conference on Decision and Control, Nice, France, 2019, pp. 2373-2378
  9. P. Ong and J. Cortés. “Event-triggered control design with performance barrier”
    Proceedings of the IEEE Conference on Decision and Control, Miami Beach, Florida, 2018, pp. 951-956
  10. P. Ong and J. Cortés. “Event-triggered interactive gradient descent for real-time multi-objective optimization”
    Proceedings of the IEEE Conference on Decision and Control, Melbourne, Australia, 2017, pp. 5445-5450