Barrier Functions in Cascaded Controller: Safe Quadrotor Control

Khan, Mouhyemen; Zafar, Munzir; Chatterjee, Abhijit

doi:10.23919/acc45564.2020.9147864

Cited by 22 publications

(10 citation statements)

References 19 publications

(51 reference statements)

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“…which takes the form (19) and satisfies Assumption 4 in the following way: the first part is satisfied by construction; the second holds since, according to (24), W (t) = t 0 e −k e (t−s) ∆(x(s))ds, and thus W is bounded for bounded ∆(x) (which is bounded for bounded x); and the third part is satisfied if N (∆(x)) is constant, though this is a sufficient and not a necessary condition.…”

Section: State Predictormentioning

confidence: 99%

See 1 more Smart Citation

Fixed-Time Parameter Adaptation for Safe Control Synthesis

Black¹,

Arabi²,

Panagou³

2022

Preprint

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We propose a fixed-time stable parameter adaptation law that guarantees that an additive, parameter-affine disturbance appearing in the dynamics of a class of nonlinear, control-affine systems is learned within a fixed time. We then provide an upper bound on the parameter estimation error as an explicit function of time, and use such knowledge to formulate a control barrier function condition to guarantee safety of the system trajectories at all times. We further show that our proposed parameter adaptation law is robust against bounded perturbations to the system dynamics in that the resulting estimated parametric disturbance converges to a known neighborhood of the true parametric disturbance within a fixed time. To illustrate the advantages of our proposed approach, we conduct a comparative numerical study against various controllers from the literature. Finally, we validate our approach on a trajectory-tracking problem subject to safety requirements using a 6 degree-of-freedom quadrotor model in an unknown wind field.

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Section: State Predictormentioning

confidence: 99%

“…In this case, we selected α = π 2 so that the quadrotor could not flip upside-down. For the nominal control input u nom , we use the tracking controller developed for quadrotors by [40] and used for safe quadrotor control in [24].…”

Section: Constant Wind Fieldmentioning

confidence: 99%

Fixed-Time Parameter Adaptation for Safe Control Synthesis

Black¹,

Arabi²,

Panagou³

2022

Preprint

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show abstract

“…The method was extended to guarantee the safety of a three-dimensional quadrotor in [10]. Khan et al proposed cascaded CBFs for a cascaded control architecture of quadrotors to enforce safety, allowing independent safety regulation in the altitude domain and in the lateral domain of a quadrotor [11]. However, [9], [10], [11] focused on quadrotors with cascaded controllers and developed cascaded CBFs for quadrotors.…”

Section: Introductionmentioning

confidence: 99%

Non-cascaded Control Barrier Functions for the Safe Control of Quadrotors

Zeng¹,

Cao²,

Liang³

et al. 2022

Preprint

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Researchers have developed various cascaded controllers and non-cascaded controllers for the navigation and control of quadrotors in recent years. It is vital to ensure the safety of a quadrotor both in normal state and in abnormal state if a controller tends to make the quadrotor unsafe. To this end, this paper proposes a non-cascaded Control Barrier Function (CBF) for a quadrotor controlled by either cascaded controllers or a non-cascaded controller. Incorporated with a Quadratic Programming (QP), the non-cascaded CBF can simultaneously regulate the magnitude of the total thrust and the torque of the quadrotor determined a controller, so as to ensure the safety of the quadrotor both in normal state and in abnormal state. The non-cascaded CBF establishes a non-conservative forward invariant safe region, in which the controller of a quadrotor is fully or partially effective in the navigation or the pose control of the quadrotor. The non-cascaded CBF is applied to a quadrotor performing trajectory tracking and a quadrotor performing aggressive roll maneuvers in simulations to evaluate the effectiveness of the non-cascaded CBF.

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“…In particular, in [24], CBFs are used to ensure that teams of quadrotors are able to fly in a collision free manner; in [18], CBFs are used for obstacle avoidance in quadrotor path planning in a surveillance scenario; and in [28], CBFs are used for flight safety for quadrotors under some degree of human control. Other works using barrier functions for UAV safety include [27,26,11]. Other applications of barrier functions include adaptive cruise control and lane keeping [4,30,29], bipedal walking robots [16,15], and collision avoidance for multirobot systems on land [25].…”

Section: Introductionmentioning

confidence: 99%

Formal verification of octorotor flight envelope using barrier functions and SMT solving

Heersink,

Sylla,

Warren

2021

Preprint

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This paper introduces an approach for formally verifying the safety of the flight controller of an octorotor platform. Our method involves finding regions of the octorotor's state space that are considered safe, and which can be proven to be invariant with respect to the dynamics. Specifically, exponential barrier functions are used to construct candidate invariant regions near desired commanded states. The proof that these regions are invariant is discovered automatically using the dReal SMT solver, which ensures the accurate command tracking of the octorotor to within a certain margin of error. Rotor failures in which rotor thrusts become stuck at fixed values are considered and accounted for via a pseudo-inverse control allocator. The safety of the control allocator is verified in dReal by checking that the thrusts demanded by the allocator never exceed the capability of the rotors. We apply our approach on a specific octorotor example and verify the desired command tracking properties of the controller under normal conditions and various combinations of rotor failures.

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Barrier Functions in Cascaded Controller: Safe Quadrotor Control

Cited by 22 publications

References 19 publications

Fixed-Time Parameter Adaptation for Safe Control Synthesis

Fixed-Time Parameter Adaptation for Safe Control Synthesis

Non-cascaded Control Barrier Functions for the Safe Control of Quadrotors

Formal verification of octorotor flight envelope using barrier functions and SMT solving

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