Sensor based robotic systems are an important emerging technology. Whenrobots are working in unknown or partially known environments, they need rangesensors that will measure the Cartesian coordinates of surfaces of objects intheir environment. Like any sensor, range sensors must be calibrated. The rangesensors can be calibrated by comparing a measured surface shape to a knownsurface shape. The most simple surface is a plane and many physical objects haveplanar surfaces. Thus, an important problem in the calibration of range sensorsis to find the best (least squares) fit of a plane to a set of 3D points.

We have formulated a constrained optimization problem to determine the leastsquares fit of a hyperplane to uncertain data. The first order necessaryconditions require the solution of an eigenvalue problem. We have shown that thesolution satisfies the second order conditions (the Hessian matrix is positivedefinite). Thus, our solution satisfies the sufficient conditions for a localminimum. We have performed numerical experiments that demonstrate that oursolution is superior to alternative methods.

There is growing interest in robots that are designed specifically to interact with people and which respond to voice commands. Very little attention has been paid, however, to the kind of verbal interaction that is possible or desirable with robots. This paper presents recent work in multimodal interfaces that addresses this question. It proposes a new form of robot-user interface, namely a collaborative conversational interface. This article explains what collaborative conversational interfaces are, argues for their application in robots, and presents strategies for designing good conversational interfaces. It concludes with a discussion of the particular challenges faced in designing conversational interfaces for robots.

1. The International Federation of Robotics expects to have a presence on the World Wide Web by the time this issue of Robotica is published. The URL will be http://www.ifr.org. The IFR Web pages will include information about the Federation's activities as well as links to its member associations in Europe, Asia, North America and Australia.

Two more IFR member associations have established home pages on the World Wide Web. BRA (formerly the British Robot Association) can be found at http://www.bra-automation.co.uk, and the Danish Industrial Robot Association (DIRA) has its home page at http://inet.uni-c.dk/~i29876.

On September 2 1996, Professor Edmond Nicolau, an eminent cybernetician and great intellect, died aged 74. This was, indeed, a great loss to the world of science. I have also lost a devoted friend and active collaborator in the fields of cybernetics and systems, as well as a valuable member of the Editorial Board of Robotica.