H-Point Machine (HPM-II)—Procedure for H-Point Determination—Benchmarking Vehicle Seats
Benchmarking is used to discover the design intent measurements for seating compartments in vehicles when these measurements are either unknown or are specified using differing measurement procedures.
This document provides the specifications and procedures to establish consistent measurements for benchmarking vehicle seating positions using the H-Point Machine (HPM-II1) described in SAE J4002 and the H-Point Design tool (HPD) described in SAE J4004. The HPM-II is a physical tool used to establish key reference points and measurements in a vehicle (Figure 1). The HPD is a CAD tool that aids in the benchmarking process (see Appendix A and SAE J4004).
The 2008 revision of this Practice relates to revisions in SAE J4004 (2008) that change the way foot and pedal reference points are established. The PRP is replaced with the BOFRP which is now a point on the shoe when the shoe is in contact with the accelerator pedal. The AHP to BOF distance was changed from 200 mm to 203 mm for better agreement with the previous SAE J826 and SAE J1100:2008.
NOTE: Some key differences from the previous version of SAE J4003 are:
Use of the SAE 95th SgRP equation with an 87 degree driver ankle angle is recommended.
When H30-1 is known, it potentially reduces the number of iterative calculations that may be required to complete the Benchmarking procedure.
Even though manufacturers are encouraged to report the driver seat height (H30), a procedure for determining H30 is now provided. When applied to seats with vertical adjustment (H21) of 40 mm or greater, H30 (and the SgRP) is established at 20 mm directly above the full down H-point travel path in order to make consistent comparisons of seating packages across vehicles. For vertical adjustment less than 40 mm, the SgRP should be established on the SgRP curve at mid-vertical H-point travel height.
This document should yield similar results to those from the SAE J826 (2008) design tool, provided that the flat shoe defined in SAE J826 is used.