On the model-based design of front-to-total anti-roll moment distribution controllers for yaw rate tracking

In passenger cars active suspensions have been traditionally used to enhance comfort through body control, and handling through the reduction of the tyre load variations induced by road irregularities. However, active suspensions can also be designed to track a desired yaw rate profile through the control of the anti-roll moment distribution between the front and rear axles. The effect of the anti-roll moment distribution relates to the nonlinearity of tyre behaviour, which is difficult to capture in the linearised vehicle models normally used for control design. Hence, the tuning of anti-roll moment distribution controllers is usually based on heuristics. This paper includes an analysis of the effect of the lateral load transfer on the lateral axle force and cornering stiffness. A linearised axle force formulation is presented, and compared with a formulation from the literature, based on a quadratic relationship between cornering stiffness and load transfer. Multiple linearised vehicle models for control design are assessed in the frequency domain, and the respective controllers are tuned through optimisation routines. Simulation results from a nonlinear vehicle model are discussed to analyse the performance of the controllers, and show the importance of employing accurate models of the lateral load transfer effect during control design

On the model-based design of front-to-total anti-roll moment distribution controllers for yaw rate tracking

In passenger cars active suspensions have been traditionally used to enhance comfort through body control, and handling through the reduction of the tyre load variations induced by road irregularities. However, active suspensions can also be designed to track a desired yaw rate profile through the control of the anti-roll moment distribution between the front and rear axles. The effect of the anti-roll moment distribution relates to the nonlinearity of tyre behaviour, which is difficult to capture in the linearised vehicle models normally used for control design. Hence, the tuning of anti-roll moment distribution controllers is usually based on heuristics. This paper includes an analysis of the effect of the lateral load transfer on the lateral axle force and cornering stiffness. A linearised axle force formulation is presented, and compared with a formulation from the literature, based on a quadratic relationship between cornering stiffness and load transfer. Multiple linearised vehicle models for control design are assessed in the frequency domain, and the respective controllers are tuned through optimisation routines. Simulation results from a nonlinear vehicle model are discussed to analyse the performance of the controllers, and show the importance of employing accurate models of the lateral load transfer effect during control design

Renal impairment in patients with inflammatory bowel disease: association with aminosalicylate therapy?

In recent years, several case reports have been published suggesting an association between the use of 5-aminosalicylic acid (5-ASA) in patients with inflammatory bowel disease (IBD) and the development of chronic tubulo-interstitial nephritis. Apart from lesions associated to 5-ASA treatment, however, it is clear that IBD itself may also induce renal impairment, albeit the frequency is unknown. During 1 year, all IBD patients seen at the outpatient clinic of 27 European centres of gastro-enterology were registered and screened for renal impairment controlling for a possible association with 5-ASA therapy. Patients were questioned about their medical and drug history and their IBD disease activity. Renal screening (calculated creatinine clearance) was performed at baseline, after 6 and 12 months. Included patients (n = 1,529) had a mean age of 39 (range 14-98), 56% had Crohn's disease, 42% ulcerative colitis and 2% indeterminate colitis. Half of the patients used 5-ASA during the study period. Decreased creatinine clearance was observed in 34 patients, among them 13 with chronic renal impairment. Comparing patients with and without renal impairment, no difference could be observed in 5-ASA consumption. In contrast, patients with renal impairment were significantly older, had a lower body mass index and showed a higher frequency of male sex, bowel resection and stoma. Although the association between 5-ASA therapy and chronic tubulo-interstitial nephritis is clearly described in several case reports, this prospective study came to the reassuring conclusion that renal impairment in IBD patients is not frequently observed and is rarely associated with 5-ASA therap