Document ID: chunk:federal_register_of_legislation:F2018C00341:body:0:p49
Version: federal_register_of_legislation:F2018C00341
Segment Type: other
Provision Reference: 
Character Range: 139885–142751

0.0005: fS, = 2 ∙ (6.69 ∙ fo), where fS, is the sampling
       frequency = 2 ∙ fN.

       2.3. Filter phase shifts and time delays for anti-aliasing filtering

        Excessive analogue filtering shall be avoided, and all filters shall have sufficiently similar phase characteristics to ensure that time delay differences are within the required accuracy for the time measurement. Phase shifts are especially significant when measured variables are multiplied together to form new variables, because while amplitudes multiply, phase shifts and associated time delays add. Phase shifts and time delays are reduced by increasing fo. Whenever equations describing the pre-sampling filters are known, it is practical to remove their phase shifts and time delays by simple algorithms performed in the frequency domain.

        Note: In the frequency range in which the filter amplitude characteristics remain flat, the phase shift Φ of a Butterworth filter can be approximated by

        Φ = 81 ∙ (f/f0) degrees for second order

        Φ = 150 ∙ (f/f0) degrees for fourth order

        Φ = 294 ∙ (f/f0) degrees for eighth order

        The time delay for all filter orders is: t = (Φ/360) ∙ (1/f0)

       2.4. Data sampling and digitising

        At 30 Hz the signal amplitude changes by up to 18 per cent per millisecond. To limit dynamic errors caused by changing analogue inputs to 0.1 per cent, sampling or digitising time shall be less than 32 μs. All pairs or sets of data samples to be compared shall be taken simultaneously or over a sufficiently short time period.

       2.5. System requirements

        The data system shall have a resolution of 12 bits (±0.05 per cent) or more and an accuracy of ±0.1 per cent (2 lbs). Anti-aliasing filters shall be of order 4 or higher and the relevant data range fmax shall be 0 Hz to 30 Hz.

        For fourth order filters the pass-band frequency fo (from 0 Hz to frequency fo) shall be greater than 2.37 ∙ fmax if phase errors are subsequently adjusted in digital data processing, and greater than 5 ∙ fmax otherwise. For fourth order filters the data sampling frequency fs shall be greater than 13.4 ∙ fo.

Appendix 2 - Attachment 6

         The following is a modified form of Annex 8 of UNECE Regulation No. 13-H– UNIFORM PROVISIONS CONCERNING THE APPROVAL OF PASSENGER CARS WITH REGARD TO BRAKING, incorporating supplement 14 to the 00 series of amendments.

SPECIAL REQUIREMENTS TO BE APPLIED TO THE SAFETY ASPECTS
OF COMPLEX ELECTRONIC VEHICLE CONTROL SYSTEMS

         1. GENERAL

          This attachment defines the special requirements for documentation, fault strategy and verification with respect to the safety aspects of Complex Electronic Vehicle Control Systems (definition 2.3. below) as far as this standard is concerned.

          This attachment does not specify the