a responsive energy absorbing ( e / a ) system constructed according to a presently preferred embodiment of the invention is shown generally at 10 in fig1 and comprises an energy absorber in the form of at least one variable , plastically deformable metal strap 12 that is anchored to one component 14 of two relatively movable components 14 , 16 reacting against a load adjuster in the form of an elongated anvil 18 carried on the second component 16 and operative to engage and deform the metal strap 12 in response to relative movement of the first and second components 14 , 16 under controlled conditions . the anvil 18 is coupled to a control system 20 which is operative to control the position of the anvil 18 relative to the strap 12 in order to change the energy absorbing characteristics of the e / a system 10 in response to various inputs , some of which are described below . [ 0015 ] fig1 shows the e / a system 10 incorporated into a steering column assembly 22 of a vehicle ( not shown ). the steering column assembly 22 includes a steering column or housing 24 surrounding a steering shaft 26 that mounts a steering wheel ( not shown ) at its upper end and is operably coupled at its lower end to a steering mechanism ( not shown ) which steers the steerable wheels of the vehicle . the steering column 24 is cradled by a lower mounting bracket 28 which is fixed by a mounting flange to support structure 32 of the vehicle ( not shown ). the mounting bracket 28 suspends the column 24 from the support structure 32 , while enabling the column 24 to collapse or slide through the bracket 28 relative to the support structure 32 in the event of a vehicle crash under circumstances in which the driver forcibly strikes the upper end of the column 24 , forcing the column to collapse relative to the support structure 32 . the e / a system 10 manages the collapse of the column 24 in such manner as to control the dissipation of energy according to certain control parameters . the overall e / a system 10 may include , in addition to the variable e / a strap 12 , one or more passive e / a straps 34 , such that the system 10 has both passive and variable e / a components . the passive e / a straps 34 may comprise , for example , one or more j - straps as illustrated in fig1 which include plastically deformable metal strips 36 each having an anchored end 38 and a free end 40 . each anchored end 38 is connected to the support structure 32 of the vehicle and by a sheerable mount 42 to a sheer bracket 44 fixed to and movable with the column 24 . the strips 36 are bent around anvils 46 on the bracket 44 . in the event of a collision , a forward movement of the column 24 relative to the support structure 32 breaks the sheerable mount 42 free of the vehicle support structure and drives the sheer bracket 44 forward with the column 24 , causing the anvils 46 to draw across the strips 36 , and in so doing dissipate a predetermined amount of energy of the load applied to the steering column 24 from the impact of the driver of the vehicle . accordingly , the e / a system 10 of the invention preferably has a passive component of energy absorption attributable to the passive straps 34 , and a supplemental active or adaptive component attributable to the strap 12 to provide further energy dissipation in addition to that provided by the passive straps 34 , depending upon input from the control system 20 which varies the energy absorption characteristics of the active or adaptive component , that is , the variable strap 12 . as shown in fig1 the active e / a strap 12 is m - shaped . legs 52 are wrapped around a set of laterally spaced stationary side anvils 49 , presenting two outer bends or loops 51 of the strap 12 . upper ends 48 of the legs 52 are free . the lower ends of the legs 52 of the strap 12 are connected by a looped or generally v - shaped portion 50 disposed between and forward of the outer loops 51 , giving the strap 12 the m - shape . the anvil 18 contacts the outer concave surface of the v - shaped portion 50 . forward movement of the column 24 , and thus the anvils 49 urges the outer surface of the v - shaped portion against the anvil 18 , causing the legs 52 of the strap 12 to bend around the anvils 49 , increasing the length of the v - shaped portion 50 . according to the invention , the engagement and reaction between the outer surface of the v - shaped portion 50 of the strap 12 and the anvil 18 is adjustable in such manner as to vary the energy absorption characteristics of the strap 12 during collapse of the column 24 . in the preferred embodiment , the anvil 18 is selectively movable in the axial direction , that is , parallel to the column 24 . more specifically , the anvil 18 is coupled to an actuator 54 which governs the movement and position of the anvil 18 under the control of a controller 56 which is incorporated in and is a part of the control system 20 . the actuator 54 preferably comprises a hydraulic piston 58 slidable in a cylinder 60 . the piston 58 is connected to the lower end of the anvil 18 . the cylinder 60 is fitted with a rapidly operating electronic solenoid valve 62 which controls the flow of hydraulic fluid to opposite sides of the piston 58 within the cylinder 60 . when the valve 62 is closed , the piston 58 cannot move . the controller 56 has sensors ( not shown ) which detect certain conditions that are present immediately after , or within milliseconds after , a crash , and generate a signal of a magnitude indicative of the amount of resistance to collapse of the steering column that is needed to best protect the driver . the signal is received by the solenoid valve which , through the cylinder 60 , moves the anvil appropriately to adjust the amount of resistance imposed by the anvil in accordance with the magnitude of the signal . various parameters that can be measured by the controller 56 at the time of and during a crash includes , for example , vehicle speed , driver weight and driver seat position , steering column stroke , etc . in response to the measured value of one or more or all of these variables , the controller 56 controls the operation of the valves 62 , and thus the position of the anvil 18 relative to the strap 12 during the crash event . the electronic solenoid valve 62 is extremely fast - acting and capable of causing adjustment of the anvil 18 by the actuator 54 while the column 24 is still collapsing . during a crash event , detected parameters may make it beneficial to fine - tune the adjustment of the position of the anvil 18 and thus modify the force - displacement curve to achieve optimum energy absorption under the given conditions . by controlling the movement of the anvil 18 relative to the strap 12 , a number of different force - displacement curves can be developed . this enables the designer of e / a systems to tailor a vehicle &# 39 ; s e / a system 10 to behave at peak performance to deliver optimum protection to the occupant of a vehicle under various crash scenarios . such a system is readily adapted to different vehicles and takes into account virtually unlimited control variables to optimize the performance of the e / a system in virtually any vehicle under virtually any crash scenario through the engineered control of the actuator 54 . referring to fig3 a force - displacement diagram is shown in which reaction force imposed by the energy absorbing system 20 of this invention is plotted in newtons along a vertical axis and steering column displacement is plotted in millimeters along a horizontal axis . in the event of a head - on collision , in which there is displacement of the steering column , the initial reaction force is shown along the section 70 of the curve and is a constant which may be approximately 4 , 000 newtons . this initial reaction force is imposed on the steering column 24 by the passive straps 34 and also by the variable strap 12 . in this initial reaction stage , the anvil 18 has been pre - positioned by the actuator 54 under the control of the solenoid valve 62 , determined by such factors as weight of the driver and driver seat position . then controller 20 senses the variables to be measured , such as vehicle speed , steering column stroke , etc ., also taking into account driver weight and position , and transmits an appropriate signal to the solenoid valve 62 which thereupon opens the hydraulic circuit in the cylinder 60 to deliver hydraulic fluid to one side or the other of the piston 58 , thus to adjust the position of the anvil 18 and in this case increase the amount of resistance force imposed on the steering column 24 to approximately 6 , 000 newtons as represented by the portion of the curve designated 72 . the increased resistance to force thus continues during the further collapse of the steering column . by using current hydraulic valve technology in the m - strap actuator 60 and an appropriate controller 20 , a force - displacement curve can be constructed of much greater complexity as indicated in fig4 in which the amount of force resistance to collapse of the steering column rises and falls as the steering column collapses . the object , of course , is to protect the driver from serious injury by a controlled resistance during the entire collapse of the steering column .