Towards Safe Learning-Based Control Performance & Constraint Satisfaction under Uncertainties Melanie Zeilinger Institute for Dynamic Systems and Control [email protected]Collaboration with: E. Klenske, P. Hennig, B. Schölkopf (MPI) K. Akametalu, J. Fisac C. Tomlin (UC Berkeley)
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Towards Safe Learning-Based ControlPerformance & Constraint Satisfaction under Uncertainties
Melanie ZeilingerInstitute for Dynamic Systems and Control
Collaboration with:E. Klenske, P. Hennig, B. Schölkopf (MPI)K. Akametalu, J. Fisac C. Tomlin (UC Berkeley)
Variable speed control of compressorsABB drives control the compressors of the world‘s longest gas export pipeline
theweek.comabb.com control.ee.ethz.ch
PerformanceSafety
Performance and SafetyGo Together
no knowledge of safety boundaries
with knowledge of safety boundaries
Video courtesy of Kene Akametalu
Variable speed control of compressorsABB drives control the compressors of the world‘s longest gas export pipeline
theweek.comabb.com control.ee.ethz.ch
Model! System dynamics
! Constraints
! Computation
PerformanceSafety
The Quest for a Good ModelModel Uncertainty
x = f (x, u, t, d) g(x, u, t, d) � 0
Complexity External effects Variation
tcadsolutions.com
autoguide.com
Optimization-based Control High Performance for Constrained Systems
6
mea
sure
men
ts
Dynamical System
control input
minN�
k=0
l(x(k), u(k)) + g(x(N))
Z�[� x(k + 1) = f (x(k), u(k), d(k))
(x(k), u(k)) � X
Standard control
Model predictive control
Optimization-based Control High Performance for Constrained Systems
7
mea
sure
men
ts
Dynamical System
control input
minN�
k=0
l(x(k), u(k)) + g(x(N))
Z�[� x(k + 1) = f (x(k), u(k), d(k))
(x(k), u(k)) � X
Rely on system model! High performance! Recursive constraint satisfaction! Stability by design! Automatic synthesis
Automatic Synthesis Of High Performance, Safe Controllers
8
Learning&
Controller
Performance &
Safety
Software/Implementation
mea
sure
men
ts
Dynamical System
control input
Environment Human
Online data
Specifications+
Online data
Learning-basedcontroller
Previous WorkReal-time Constraints in Optimization-based Control
9
ControllerPerformance
& Safety
Software/Implementation
! Real-time model predictive control [Zeilinger et al., 2008 – 2014]
! High-speed, certified optimization [Domahidi, Z. et al., 2012; Pu, Z. et al., 2014, 2016]
mea
sure
men
ts
Dynamical System
control input
minN�
k=0
l(x(k), u(k)) + g(x(N))
Z�[� x(k + 1) = f (x(k), u(k), d(k))
(x(k), u(k)) � X
Software/Specifications+
Online data
Outline
10
mea
sure
men
ts
Dynamical System
control input
Environment Human
Online data
This talk:! Learning for performance: Tailoring optimal controllers online ! Safety guarantees: Constraint satisfaction for any performance controller12
Learning-basedcontroller
Outline
11
mea
sure
men
ts
Dynamical System
control input
Environment Human
Online data
This talk:! Learning for performance: Tailoring optimal controllers online ! Safety guarantees: Constraint satisfaction for any performance controller12
minN�
k=0
l(x(k), u(k)) + g(x(N))
Z�[� x(k + 1) = f (x(k), u(k), d(k))
(x(k), u(k)) � X
How to predict complex behavior, quantify & reduce
uncertainties?
Quantifying Uncertain Predictions From Online Data
12
estimated RegressionDynamical
Model
Infer function d (t ) online:
measured states
applied inputs
{x(t k)}Kk=0
{u(t k)}Kk=0
�d(t k)
� Kk=0
inferred function d(t )
e.g. x(k + 1 )
= f (x(k ), u(k )) + d(x, u, k )
x(k + 1) = f (x(k), u(k), d(k))
d
x 1 x2
Quantifying Uncertain Predictions From Online Data Using Gaussian Process Regression
13
meanfunction
variance
measured states
applied inputs
estimated GPRegression
Dynamical Model
{x(t k)}Kk=0
{u(t k)}Kk=0
d(t )
� 2d (t )
" Predictive distribution
Infer function d (t ) online:
GP prior: mean + covariance fcn
d(t )
2 �d (t )
d(t )
t
�d(t k)
� Kk=0
x(k + 1) = f (x(k), u(k), d(k))
Quantifying Uncertain Predictions From Online Data Using Gaussian Process Regression
14
meanfunction
variance
measured states
applied inputs
estimated GPRegression
Dynamical Model
{x(t k)}Kk=0
{u(t k)}Kk=0
d(t )
� 2d (t )
Infer function d (t ) online:
GP prior: mean + covariance fcn
�d(t k)
� Kk=0
Examples:! Mechanical errors! Prediction of loads, efficiencies etc. in energy systems! Unknown nonlinear dynamics (e.g. ground effects)
Gears Cause Periodic Errorsexample: astrophotography
1
" Predictive distribution
x(k + 1) = f (x(k), u(k), d(k))
Example:Telescope Guiding
Photograph by Robert Vanderbei, La Palma, 2012
Quantifying Uncertain Predictions From Online Data Using Gaussian Process Regression
16
meanfunction
variance
measured states
applied inputs
estimated GPRegression
Dynamical Model
{x(t k)}Kk=0
{u(t k)}Kk=0
d(t )
� 2d (t )
Infer function d (t ) online:
Gaussian Process regression with ‘weakly periodic’ kernel
�d(t k)
� Kk=0
linear system + gear effectx(k + 1 ) = A x(k ) + B u(k ) + d(k )
Comparison to State of the ArtOpen Source Software PHD Guiding by Edgar Klenske
17currently own branch on github.com/OpenPHDGuiding/phd2
0 500 1,000 1,500 2,000 2,500 3,000 3,500�2�1
012
errorRA
[px]
Tracking Algorithm of PHD2 Guiding 2.5.0
0 500 1,000 1,500 2,000 2,500 3,000 3,500�2�1
012
errorRA
[px]
Tracking with GP Prediction
RMS(e) = 0.4174
RMS(e) = 0.3080
26% reduction
erro
r RA
[px]
erro
r RA
[px]
26% reduction
time [s]
Tracking Algorithm of PHD2 Guiding 2.5.0
Tracking with GP Prediction
RMS(error) = 0.4174
RMS(error) = 0.3080
Tracking in “Darkness”Robustness through Improved Predictions
This talk:! Learning for performance: Tailoring optimal controllers online ! Safety guarantees: Constraint satisfaction for any performance controller12