Nonlinear robust controller design for multi-robot systems with unknown payloads

This work is concerned with the control problem of a multi-robot system handling a payload with unknown mass properties. Force constraints at the grasp points are considered. Robust control schemes are proposed that cope with the model uncertainty and achieve asymptotic path tracking. To deal with the force constraints, a strategy for optimally sharing the task is suggested. This strategy basically consists of two steps. The first detects the robots that need help and the second arranges that help. It is shown that the overall system is not only robust to uncertain payload parameters, but also satisfies the force constraints

PARTISAN POLITICS, INTEREST RATES AND THE STOCK MARKET: EVIDENCE FROM AMERICAN AND BRITISH RETURNS IN THE TWENTIETH CENTURY

We examine the relationship between government partisanship, interest rates and the mean and volatility of stock prices in the United States and United Kingdom. We suggest that traders in the stock market rationally expect higher (lower) post-electoral interest rates during the incumbency of the left-wing (right-wing) party - Democrats and Labor (Republican and Conservative) - and in election years when they expect the left-wing (right-wing) party to win elections. We hypothesize that expectations of higher (lower) interest rates decrease (increase) the mean and volatility of stock prices during the actual incumbency or even anticipation of a left-wing (right-wing) party holding the office of the chief executive. Results from empirical models estimated on data from U.S. and U.K. markets over most of the twentieth century statistically support our claims. Copyright 2007 Blackwell Publishing Ltd..