VDIM enhances handling, traction and braking systems that normally react to vehicle driving conditions by anticipating tire slippage before a skid, slide or wheel spin occurs and making corrections in a smooth, progressive way. This ability, coupled with tight integration of all dynamic systems, makes VDIM feel transparent to the driver and driving more enjoyable. To do this, VDIM uses an active control strategy that takes its cues from a comprehensive range of sensors including steering angle, yaw rate, deceleration, brake pressure, brake pedal stroke, wheel speed and others. Their signals are used individually by the various traction control systems and collectively by VDIM. Data are gathered from more sources and processed rapidly, helping to make VDIM less obtrusive yet highly effective. These proven systems include Vehicle Stability Control (VSC), Traction Control (TRC), Brake Assist (BA), Anti-Lock Brakes (ABS) and Electronic Throttle Control with intelligence (ETC-i). In addition, three important new technologies are employed that are central to the effectiveness of VDIM: Electric Power Steering (EPS), Electronically Controlled Brakes (ECB), and in the GS 430 only, Variable Gear Ratio Steering (VGRS). VDIM then integrates all of these elements with powerful proprietary software to help seamlessly manage the total vehicle dynamic package. TECB is one of the key new technologies that make VDIM possible. It's a "brake-by-wire" system that translates brake pedal pressure into electric signals that, via computer control, help provide precise and optimized braking control in virtually any traction condition. The ECB system is also backed by conventional hydraulic brake control in the unlikely event of electronic failure. ECB's electronic control provides quick brake response when needed, which helps the VDIM system to anticipate and help correct skids before they happen. VGRS Adds New Dimensions to GS 430 Although new in this application (on GS 430 only), VGRS is a further development of the technology recently introduced on the Lexus LX 470. VGRS provides several benefits, including active steering, that enhance driving pleasure and control in a seamless manner. First, it provides a relatively quick steering ratio in very low speed conditions, which notably improves maneuverability for parking and similar situations. From low to medium speeds the steering ratio progressively slows to levels more appropriate for driver comfort in city driving. In higher speed conditions such as freeway driving, the steering ratio is reduced even further to help provide a more secure and comfortable feel for the driver. Another important function of VGRS is called "differential steering control" which helps the steering system correct for a slight delay in steering response—something that occurs in all vehicles. This function helps enhance driving feel in lane changes and other transitional situations. Perhaps most importantly, in difficult driving conditions VGRS interacts with other systems via VDIM to actively and automatically apply subtle changes in steering angle ratio and effort in order to assist the driver in maintaining smooth control, even in side winds, all while remaining virtually transparent to the driver. Electronic Assist = Steering Feel With Intelligence EPS is yet another important steering development that makes contributions to driving feel and controllability in the GS 430, RX 400h and Highlander Hybrid. Rather than using the purely passive hydraulic assist found in conventional power steering systems, EPS uses precise electronic assist via the built-in DC motor in the steering gear housing. The assist is computer controlled to help provide comfortable and controllable levels of steering effort in most driving situations. With VDIM interaction, the amount of assist can be instantly varied for the conditions at hand. By eliminating the engine-driven hydraulic pump, EPS also reduces fuel consumption. And stripped of the usual hydraulic system of pump, hoses, pipes and fluid, the simplified steering gear is lighter and more compact than conventional power steering systems. With all of the traction control technologies working together under the VDIM "umbrella," handling smoothness is dramatically enhanced. Whether driving through town or enthusiastically on a winding road, the VDIM system works constantly and seamlessly to maintain comfort and driving balance, without spoiling the fun. # # # Source: Toyota |