The purpose of this paper is to highlight the increasing use of rotary or angle encoders and examine two distinct types of non‐contact encoders that employ novel technologies to meet the demands of very different applications.
Firstly, examines the design characteristics of optical angle encoders which are used for precision applications such as rotary format computer‐to‐plate pre‐press machines, machine tool A, B and C axes, and surface mount machines. Then considers magnetic encoder design, including the latest OnAxis™ technology for lower cost applications which require less precision, but are often more physically demanding.
Different rotary motion applications demand different combinations of performance and features to optimise their function – some require accuracy, others repeatability, high‐resolution or low‐cyclic error for velocity loop control, plus cost can also be a key consideration.
There is an increasing need to control rotary motion. An appreciation of the design principles of optical angle and rotary magnetic encoders is necessary to ensure that the correct choice of encoder is made for each application. For an angle encoder system, trade‐offs should be made to determine a realistic specification, and whilst many factors can limit achievable accuracy, techniques are available for reducing any shortfall. For applications where cost constraints and lower accuracy specifications demand a magnetic encoder, robust OnAxis™ sensor technology is gaining acceptance amongst designers, and whilst many of the basic design principles of optical encoders still apply, other specific technical aspects, such as much lower resolution and accuracy must be understood before using these devices. Hidden design costs should also be understood such as installation timings and the environmental suitability of magnets.
Will aid designers of rotary motion systems to make a well‐informed selection of encoder type, based on the detailed needs of their applications, including accuracy and cost budgets.
Investigates urban bias in state policy making in Mexico. Refers to literature claiming that rural poverty in developing nations is a major problem because capitalism…
Investigates urban bias in state policy making in Mexico. Refers to literature claiming that rural poverty in developing nations is a major problem because capitalism reflects an urban bias. Examines social security coverage for the rural poor in Mexico and notes that there are great variations depending on area, suggesting that social security coverage is politically negotiable. Outlines briefly the historical development of Mexico’s welfare state and uses a power resource model to demonstrate how groups with competing interests go about securing benefits from the state. Cites literature on dependency theory, indicating that rural groups have failed to mobilize politically and have therefore not secured the same state resources (such as social security benefits and housing) as urban groups, yet argues that this does not always apply in Mexico, partially due to party politics and bureaucratic paternalism. Explains how data was collected to examine regional variations in social security coverage among the rural poor and how the data was analysed. Reveal that workers in important international export markets (such as cotton and sugar) have greater political leverage in obtaining better social security benefits. Notes also that areas supporting the political party in power obtain better benefits. Concludes, therefore, that rural workers are not powerless in the face of urban capitalism and that urban bias and dependency theories do not reflect the situation in Mexico – rather social security benefits are politically negotiable.
This study explores the simultaneous transitions in Palestine/Israel and South Africa at the end of the 20th century through an analysis of the shifting geography of…
This study explores the simultaneous transitions in Palestine/Israel and South Africa at the end of the 20th century through an analysis of the shifting geography of Johannesburg and Jerusalem. After analyzing the relationship between political, economic and spatial restructuring, I examine the walled enclosures that mark the landscapes of post-apartheid Johannesburg and post-Oslo Jerusalem. I conclude by arguing that these walled enclosures reveal several interconnected aspects of the relationship between neo-liberal restructuring and the militarization of urban space. They also exemplify different configurations of sovereignty under conditions of neo-liberalism and empire.