A subframe assembly for a vehicle and a method for manufacturing the same is disclosed. The subframe assembly includes a crossmember, a straight arm, and a side bracket. The crossmember includes an end bracket disposed at an end thereof. The straight arm is received into and metallurgically bonded to the end bracket of the crossmember. The side bracket includes a base, and a rear bracket arm. The base is metallurgically bonded to a side of the straight arm adjacent to the end of the crossmember. The rear bracket arm extends from an end of the base and defines a hole adapted to receive a screw or pin for connecting a control arm of a wheel suspension to the subframe assembly. The rear bracket arm is at least partially received into and metallurgically bonded to the end bracket of the crossmember.

A composite material bush may include a center plate; and an outer foam which is arranged outside the center plate to surround the center plate and is made of different kinds of materials.

A rocking arm structure includes an arm body, a motive wheel assembly connected to the arm body, a caster wheel assembly connected to the arm body, and a shaft assembly connected to the arm body and disposed between the motive wheel assembly and the caster wheel assembly. The two wheel assemblies are configured to revolve in a same direction around the shaft assembly and for example allow a 4-wheeled vehicle/robot to become a 6-wheeled vehicle for stability as required during changes of terrain.

A rocking arm structure includes an arm body, a motive wheel assembly connected to the arm body, a caster wheel assembly connected to the arm body, and a shaft assembly connected to the arm body and disposed between the motive wheel assembly and the caster wheel assembly. The two wheel assemblies are configured to revolve in a same direction around the shaft assembly and for example allow a 4-wheeled vehicle/robot to become a 6-wheeled vehicle for stability as required during changes of terrain.

A leading-edge steering system is provided for a front suspension of an off-road vehicle. The leading-edge steering system is comprised of a spindle assembly that supports a drive axle assembly to conduct torque from a transaxle to a front wheel. A first rod-end joint pivotally couples an upper suspension arm and the spindle assembly, and a second rod-end joint pivotally couples a lower suspension arm and the spindle assembly. A steering rod-end joint pivotally couples a first end of a steering rod with a leading-edge portion of the spindle assembly. A steering gear is coupled with a second end of the steering rod and configured to move the steering rod, such that the spindle assembly rotates with respect to the upper and lower suspension arms. The leading-edge portion is configured to exert primarily tensile forces on the steering rod during travel over rough terrain.

A leading-edge steering system is provided for a front suspension of an off-road vehicle. The leading-edge steering system is comprised of a spindle assembly that supports a drive axle assembly to conduct torque from a transaxle to a front wheel. A first rod-end joint pivotally couples an upper suspension arm and the spindle assembly, and a second rod-end joint pivotally couples a lower suspension arm and the spindle assembly. A steering rod-end joint pivotally couples a first end of a steering rod with a leading-edge portion of the spindle assembly. A steering gear is coupled with a second end of the steering rod and configured to move the steering rod, such that the spindle assembly rotates with respect to the upper and lower suspension arms. The leading-edge portion is configured to exert primarily tensile forces on the steering rod during travel over rough terrain.

A suspension characteristic is changed depending on a travel state by a simple structure. An ECU uses a vehicle speed-spring constant setting part to calculate a target spring constant depending on a vehicle speed, and uses a spring constant-frequency setting part to calculate a set frequency corresponding to the target spring constant. An oscillation input calculation part generates a signal representing an oscillation input oscillating at the set frequency. A superimposition part sets a value acquired by superimposing the oscillation input on a target driving force to a new target driving force. As a result, the wheel exhibits a minute oscillation in a longitudinal direction, resulting in an input of the minute oscillation to a suspension bush. The suspension bush changes in a spring constant and a damping coefficient depending on the frequency of the input minute oscillation. As a result, the suspension characteristic can be changed.

A suspension characteristic is changed depending on a travel state by a simple structure. An ECU uses a vehicle speed-spring constant setting part to calculate a target spring constant depending on a vehicle speed, and uses a spring constant-frequency setting part to calculate a set frequency corresponding to the target spring constant. An oscillation input calculation part generates a signal representing an oscillation input oscillating at the set frequency. A superimposition part sets a value acquired by superimposing the oscillation input on a target driving force to a new target driving force. As a result, the wheel exhibits a minute oscillation in a longitudinal direction, resulting in an input of the minute oscillation to a suspension bush. The suspension bush changes in a spring constant and a damping coefficient depending on the frequency of the input minute oscillation. As a result, the suspension characteristic can be changed.

Methods and systems are provided for an electric heavy-duty vehicle. In one example, a system for the vehicle may include a wheel hub assembly coupled to a frame of the vehicle via a first wishbone arm and a second wishbone arm, and an air spring coupled at opposite ends to a first link and a second link, each of the first link and the second link being pivotably coupled to the frame of the vehicle, the second link further being pivotably coupled to the first wishbone arm. The air spring may be positioned above the wheel hub assembly with respect to the vehicle.

Methods and systems are provided for an electric heavy-duty vehicle. In one example, a system for the vehicle may include a wheel hub assembly coupled to a frame of the vehicle via a first wishbone arm and a second wishbone arm, and an air spring coupled at opposite ends to a first link and a second link, each of the first link and the second link being pivotably coupled to the frame of the vehicle, the second link further being pivotably coupled to the first wishbone arm. The air spring may be positioned above the wheel hub assembly with respect to the vehicle.