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

Last updated: August 2025

Papers Submitted

We have submitted a new manuscript titled "Matrix Control Barrier Functions" to the IEEE Transactions on Automatic Control. This paper introduces a novel generalization of the control barrier function framework based on matrix inequalities.

See Paper See Experiment Video
August 2025
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Papers Accepted

Two papers were accepted to the IEEE Conference on Decision and Control (CDC) 2025.

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July 2025
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Conference Travel

I will be in Denver, Colorado to attend and present at the American Control Conference (ACC) 2025.

July 2025
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NEXTCOM Feature

NEXTCOM featured me in their Meet-the-Leaders series on LinkedIn! I'm honored to be recognized as part of the next generation of researchers in the control community.

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June 2025
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Paper Accepted

The paper was accepted to the IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) 2025.

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June 2025
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Conference Travel

I will be in Atlanta, Georgia for ICRA 2025, where I am co-organizing the ICRA Workshop on Robot Safety under Uncertainty from “Intangible” Specifications.

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May 2025

Papers Submitted

We submitted two papers to the IEEE Conference on Decision and Control (CDC) 2025.

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March 2025

Paper Submitted

We submitted a paper to the IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) 2025.

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March 2025
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Joined NEXTCOM Leadership

I joined the leadership team of NEXTCOM as a CDC Ambassador. NEXTCOM is an initiative by the IEEE Control Systems Society to support and connect young professionals in control, empowering them to become the next generation of established researchers and engineers.

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January 2025
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Papers Accepted

Two papers were accepted to the American Control Conference (ACC) 2025.

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January 2025

Conference Travel

I will be in Milan, Italy to attend and present at the IEEE Conference on Decision and Control (CDC) 2024.

December 2024

Workshop Travel

I will be in Abu Dhabi, UAE to participate in the GENZERO Workshop, organized by the Technology Innovation Institute (TII).

November 2024

Papers Submitted

We submitted two papers to the American Control Conference (ACC) 2025.

See Paper 1 See Paper 2
September 2024

Papers Accepted

Two papers were accepted to the IEEE Conference on Decision and Control (CDC) 2024.

See Paper 1 See Paper 2
July 2024

Conference Travel

I will be in Toronto, Canada to attend and present at the American Control Conference (ACC) 2024.

July 2024

Papers Submitted

We submitted two papers to the IEEE Conference on Decision and Control (CDC) 2024.

See Paper 1 See Paper 2
March 2024

Papers Accepted

Two papers were accepted to the American Control Conference (ACC) 2024.

See Paper 1 See Paper 2
January 2024
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Journal Paper Published

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

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December 2023
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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.

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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
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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

Papers Submitted

We submitted two papers to CDC 2022.

See Paper 1 See Paper 2
March 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 “Nonsmooth control barrier function design of continuous constraints for network connectivity maintenance” to International Journal of Robotics Research.

See Paper
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

Paper Accepted

Our paper “Network Connectivity Maintenance via Nonsmooth Control Barrier Functions” is accepted to CDC 2021. Catch me at the conference!

CDC 2021
July 2021

Paper Submitted

We submitted a paper “Network Connectivity Maintenance via Nonsmooth Control Barrier Functions” to CDC 2021.

See Abstract
March 2021
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Paper Published

Our paper “Opportunistic robot control for interactive multiobjective optimization under human performance limitations” is published in Automatica!

See Paper
December 2020

Research Interests

Our research addresses three critical aspects of autonomous systems: safety, resource efficiency, and resiliency. These considerations are increasingly important as autonomous systems operate in complex, uncertain, and resource-constrained environments. We develop control-theoretic methods that provide formal guarantees of correct system behavior — ensuring safety through control barrier functions, reducing control and sensing demands through resource-aware strategies like event-triggered control, and maintaining reliable operation in the face of sensor failures or malicious attacks. While our methods are broadly applicable across domains, we are particularly interested in applications to aerospace and robotic systems, where autonomy under constraints is both challenging and essential. As the field increasingly embraces machine learning for performance, our work reinforces the enduring role of control theory in enabling autonomy that is verifiable and trustworthy.

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.

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.

As autonomous systems are increasingly deployed in uncertain, adversarial, or failure-prone environments, ensuring resilience — the ability to maintain safety despite component faults or malicious attacks — is crucial. For example, rather than using all available sensors to maximize state estimation performance, one line of our work investigates fault tolerance that is sufficient for safe operation under noise, failures, or sensor spoofing attacks. This work departs from traditional performance-centric paradigms and instead prioritizes formal safety guarantees, ensuring that the system behaves correctly even under uncertainty or partial observability. We have developed the secured safety filter to address sensor anomalies, and we look forward to developing a broader fault-tolerant safety framework using control barrier functions.

Whether it's a team of drones performing collaborative tasks or a constellation of satellites coordinating in orbit, many autonomous systems operate not in isolation, but as part of a network of agents. Our research explores the challenges and opportunities in controlling such multi-agent systems under safety, communication, and resource constraints. We are particularly interested in leveraging control barrier functions and decision-making strategies to ensure guaranteed safety and coordination across agents. Our work also investigates how to preserve key group objectives, such as connectivity and collision avoidance, while minimizing communication and computation overhead.

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. P. Ong, Y. Xu, R. M. Bena, F. Jabbari, and A. D. Ames. Matrix Control Barrier Functions
    IEEE Transactions on Automatic Control, submitted.
  2. P. Ong, M. H. Cohen, T. G. Molnar, and A. D. Ames. Rectified control barrier functions for high-order safety constraints
    IEEE Control Systems Letters, 8:2949–2954, 2024.
  3. P. Ong, J. Cortés Performance-barrier-based event-triggered control with applications to network systems
    IEEE Transactions on Automatic Control, 69(7), 2024.
  4. 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, 2023.
  5. P. Ong, B. Capelli, L. Sabattini, J. Cortés. Nonsmooth control barrier function design of continuous constraints for network connectivity maintenance
    Automatica, 156:111209, 2023
  6. 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)
  7. P. Ong and J. Cortés. Opportunistic robot control for interactive multiobjective optimization under human performance limitations
    Automatica 123:109253, 2021

Conference Papers

  1. X. Tan, P. Ong, P. Tabuada, and A. D. Ames. “Secure safety filter design for sampled-data nonlinear systems under sensor spoofing attacks”
    Proceedings of the IEEE Conference on Decision and Control, Rio De Janeiro, Brazil, December 2025. To Appear.
  2. P. Ong, M. H. Cohen, T. G. Molnar, and A. D. Ames. “On the properties of optimal-decay control barrier functions”
    Proceedings of the IEEE Conference on Decision and Control, Rio De Janeiro, Brazil, December 2025. To Appear.
  3. X. Tan, J. Sundar, R. Bruzzone, P. Ong, W. T. Lunardi, M. Andreoni, P. Tabuada, and A. D. Ames. “Secure safety filter: Towards safe flight control under sensor attacks”
    Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems, Hangzhou, China, October 2025. To Appear.
  4. X. Tan, P. Ong, P. Tabuada, and A. D. Ames. “Computationally efficient safe control of linear systems under severe sensor attacks”
    Proceedings of the American Control Conference, Denver, Colorado, July 2024. To Appear.
  5. P. Ong, M. H. Cohen, T. G. Molnar, and A. D. Ames. “Rectified control barrier functions for high-order safety constraints”
    Proceedings of the American Control Conference, Denver, Colorado, July 2025.
  6. P. Ong, M. Mazo Jr., and A. D. Ames. “Hierarchical event-triggered systems: Safe learning of quasi-optimal deadline policies”
    Proceedings of the IEEE Conference on Decision and Control, Milan, Italy, December 2024, pp. 4455-4461.
  7. X. Tan, P. Ong, P. Tabuada, and A. D. Ames. “Safety of linear systems under severe sensor attacks”
    Proceedings of the IEEE Conference on Decision and Control, Milan, Italy, December 2024, pp. 336-342.
  8. 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, pp. 5169-5176.
  9. 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.
  10. 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, pp. 870-877.
  11. 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.
  12. 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.
  13. 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)
  14. 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)
  15. 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.
  16. 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.
  17. 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.