Non linear system identification : a state-space approach

In this thesis, new system identication methods are presented for three particular types of nonlinear systems: linear parameter-varying state-space systems, bilinear state-space systems, and local linear state-space systems. Although most work on nonlinear system identication deals with nonlinear input-output descriptions, this thesis focuses on state-space descriptions. State-space systems are considered, because they are especially suitable for dealing with multiple inputs and outputs, and they usually require less parameters to describe a system than input-output descriptions do. Equally important, the starting point of many nonlinear control methods is a state-space model of the system to be controlled

Identification of nonlinear state-space systems using zero-input responses

This paper studies the generalization of linear subspace identification techniques to nonlinear systems. The basic idea is to combine nonlinear minimal realization techniques based on the Hankel operator with embedding theory used in time-series modeling. We show that under the assumption of zero-state observability, a collection of several zero-input responses can be used to construct a state sequence of the nonlinear system. This state sequence can then be used to estimate a state-space model via nonlinear regression. We also discuss how the zero-input responses can be obtained. The proposed method is illustrated using a pendulum as an example system.

Identification of Non-linear Nonautonomous State Space Systems from Input-Output Measurements

This paper presents a method to determine a nonlinear state-space model from a finite number of measurements of the inputs and outputs. The method is based on embedding theory for nonlinear systems, and can be viewed as an extension of the subspace identification method for linear systems. The paper describes the underlying theory and provides some guidelines for using the method in practice. To illustrate the use of the identification method, it was applied to a second-order nonlinear system

From Physical to Cyber: Escalating Protection for Personalized Auto Insurance

Nowadays, auto insurance companies set personalized insurance rate based on data gathered directly from their customers' cars. In this paper, we show such a personalized insurance mechanism -- wildly adopted by many auto insurance companies -- is vulnerable to exploit. In particular, we demonstrate that an adversary can leverage off-the-shelf hardware to manipulate the data to the device that collects drivers' habits for insurance rate customization and obtain a fraudulent insurance discount. In response to this type of attack, we also propose a defense mechanism that escalates the protection for insurers' data collection. The main idea of this mechanism is to augment the insurer's data collection device with the ability to gather unforgeable data acquired from the physical world, and then leverage these data to identify manipulated data points. Our defense mechanism leveraged a statistical model built on unmanipulated data and is robust to manipulation methods that are not foreseen previously. We have implemented this defense mechanism as a proof-of-concept prototype and tested its effectiveness in the real world. Our evaluation shows that our defense mechanism exhibits a false positive rate of 0.032 and a false negative rate of 0.013.Comment: Appeared in Sensys 201

ivPair: context-based fast intra-vehicle device pairing for secure wireless connectivity

The emergence of advanced in-vehicle infotainment (IVI) systems, such as Apple CarPlay and Android Auto, calls for fast and intuitive device pairing mechanisms to discover newly introduced devices and make or break a secure, high-bandwidth wireless connection. Current pairing schemes are tedious and lengthy as they typically require users to go through pairing and verification procedures by manually entering a predetermined or randomly generated pin on both devices. This inconvenience usually results in prolonged usage of old pins, significantly degrading the security of network connections. To address this challenge, we propose ivPair, a secure and usable device pairing protocol that extracts an identical pairing pin or fingerprint from vehicle\u27s vibration response caused by various factors such as driver\u27s driving pattern, vehicle type, and road conditions. Using ivPair, users can pair a mobile device equipped with an accelerometer with the vehicle\u27s IVI system or other mobile devices by simply holding it against the vehicle\u27s interior frame. Under realistic driving experiments with various types of vehicles and road conditions, we demonstrate that all passenger-owned devices can expect a high pairing success rate with a short pairing time, while effectively rejecting proximate adversaries attempting to pair with the target vehicle

Efficacy of dose-escalated chemoradiation on complete tumour response in patients with locally advanced rectal cancer (RECTAL-BOOST); a phase 2 randomised controlled trial

Purpose Pathological complete tumour response following chemoradiation in patients with locally advanced rectal cancer (LARC) is associated with favourable prognosis and allows organ-sparing treatment strategies. We aimed to investigate the effect of an external radiation boost to the tumour prior to chemoradiation on pathological or sustained clinical complete tumour response in LARC. Methods and materials This multicentre, non-blinded, phase 2, randomised controlled trial followed the trials within cohorts-design, which is a pragmatic trial design allowing cohort participants to be randomized for an experimental intervention. Patients in the intervention group are offered the intervention (and can accept or refuse this), whereas patients in the control group are not notified about the randomisation. Participants of a colorectal cancer cohort referred for chemoradiation of LARC to either of two radiotherapy centres were eligible. Patients were randomised to no boost or an external radiation boost (5 x 3 Gy) without concurrent chemotherapy directly followed by standard pelvic chemoradiation (25 x 2 Gy with concurrent capecitabine). The primary outcome was pathological complete response (pCR, i.e. ypT0N0) in patients with planned surgery at 12 weeks or, as surrogate for pCR, a 2-year sustained clinical complete response for patients treated with an organ preservation strategy. Analyses were intention to treat. The study was registered with ClinicalTrials.gov, number NCTXXXXXX. Results Between Sept 2014 and July 2018, 128 patients were randomised. Fifty-one of the 64 (79.7%) patients in the intervention group accepted and received a boost. Compared with the control group, fewer patients in the intervention group had a cT4-stage and a low rectal tumour (31.3% versus 17.2% and 56.3% versus 45.3% respectively), and more patients had a cN2-stage (59.4% versus 70.3% respectively). Rate of pathological or sustained clinical complete tumour response was similar between the groups: 23 of 64 (35.9%, 95%CI 24.3-48.9) in the intervention group versus 24 of 64 (37.5%, 95%CI 25.7-50.5) in the control group (OR=0.94 95%CI 0.46-1.92). Near-complete or complete tumour regression was more common in the intervention group: 34 of 49 (69.4%) versus 24 of 53 (45.3%) in the control group (OR=2.74, 95%CI 1.21-6.18). Grade >3 acute toxicity was comparable: 6 of 64 (9.4%) in the intervention group versus 5 of 64 (7.8%) in the control group (OR=1.22 95%CI 0.35-4.22). Conclusion Dose escalation with an external radiotherapy boost to the tumour prior to neoadjuvant chemoradiation did not increase the pathological or sustained clinical complete tumour response rate in LARC