DBO Check List

• 4 Regarding positioning, accuracy is how closely a system in motion approaches a command position; precision refers to the error between successive attempts to move to the same location; resolution is the smallest move increment that can be achieved
• 4 Precision means repeatability within a system, and is determined by both resolution and accuracy
• 4 Precision and accuracy requirements vary by industry; in semiconductor manufacturing, accuracy demands can be in the nanometer range
• 4 Know thine enemies — errors due to instability, errors in response to external disturbances, and errors stemming from mechanical transmission components
• 4 The most common transmission errors are from lead screws — backlash and nonlinearity
• 4 To handle disturbances, designers should make their system stiff and responsive, meaning the control loop must have high gain to make it reject disturbances
• 4 A system's ability to reject disturbances is related to bandwidth — if the system can follow command signals at high frequencies, it can reject equally dynamic disturbances
• 4 With regard to component interaction and system accuracy, remember that the whole is more than the sum of the parts; system accuracy can be improved by careful attention to component interactions
• 4 Transmitting motion over a distance inherently reduces accuracy, especially when motion is transmitted through linkages such as couplings, gearboxes, belts, and screws
• 4 Proper cabling and shielding can protect against electrical noise, optimizing accuracy
• 4 Consider materials like ceramics, glass, and engineered plastics for strength and corrosion resistance, which improves precision
• 4 Think about linear motors and direct drive systems to simplify the transmission chain and reduce system error
• 4 Integrated rack-and-pinion systems also lessen error from tolerance stack, boosting precision and accuracy